So, I started to look into the statement regarding the advertisement of the power of the C63 AMG, vs the other cars that came equipped with the same engine and how this was understated and so on.
Let;s start with this:
1 PS (Pferdestarke) does not equal 1 HP, (horsepower), it is less.
So sifting through all the magazine records, tests and so on, some from Australia as well, where they have the bhp (brakehorsepower), here is what I see:
The W211 E63 AMG came with 518 PS, this is exactly 507 HP
The ML63 AMG with M156 came with 503 HP
The R63 had 507 HP. In Germany, the R63 had 510 PS, so 503 HP.
The CLK63 even in Black series came with 500 HP
The GL63 came with 503 HP

So, I have a new set of conclusions:
The 507 has already all the factory is willing to pump out of the M156.
It is not possible to use a more advanced factory tune and flash it to the 507 to make it make more power within the safety of a factory tune and more or less guarantee that the car now has 520 HP like the vehicle that the tune is borrowed from.
The C63 Black series, for the minor 3HP bump up, probably has different hardware. I'll review the factory exhaust manifolds and catalytic converter part numbers.

So the tuners went somewhere else, in order to bring a stock car to 530 HP, via a tune only.

"stated numbers" remember that...but exhaust packaging my play a role.

I do believe that the era of stated numbers has ended in 2007, I think. That year, every manufacturer was sent to DOT to certify the numbers of their cars. And the forums were on fire. Some cars picked up 2-3 HP, some lost 7.
I think that the Sti went from a round 300 HP number in 2006 to 293 or so.

Don't forget the DR520 C63 in the UK, 513 bhp . https://www.autocar.co.uk/car-review...-c63-amg-dr520

It does, to a surprising degree from the cases I've heard about (we are talking factory here).

I think i'm confused here with the . So the general consensus was that tuners were just putting 507 tunes on every car lol. 507's dont even feel noticeably faster than a 480hp p30/p31 car.

when you're at HP levels past 380hp you don't notice 10hp additions really. this exponentially gets worse the higher in HP you go. at 500HP, you won't feel it until you add 30-50hp...at 600hp its even higher than that.

They should just do that - my 507 feels just as powerful but much more drivable then my base c63 with a tune.

It's the same in the Subaru world.
In general, tuners like to do a tune based on changing AFR. The factory works based on timing. Working on timing requires insider information and sometimes not minding blowing up a few engines , which the factory doesn't mind.
I think the factory tune has rich AFR and gets good torque.

ignition timing is done by monitoring individual knock sensor output as well as use of audible knock sensors. this along with a test room to alter air temperature, humidity, and engine load is how you build a ignition timing map. if you are turbo monitoring of exhaust gas temps play a role as well.

cam timing maps are altered based off power output and engine performance

air fuel maps are altered based off power output, engine performance, expected and resulting afr's, and at times emissions.

agreed 507/p30 tune feels much better than most aftermarket tunes.

and to the other guy while yes 10-20hp isnt as noticeable at 500hp as its only a 5% increase at that power level vs being a 20% increase on a 100hp civic lol. Ive driven plenty of cars, fast and slow, plenty for accurate comparison. Torque absolutely matters. Take my car for example it makes 40whp more than the top all motor 63 guys that seems like **** because its supercharged lol, yet it feels like a rocket because of the 534wtq and where the none peak gains take place. Torque does matter but it's just half the picture. compare a 570hp sls and a 590hp sls gt - 20hp difference on paper. Massive power difference same "alleged" torque. We all know factory numbers are BS anyways. you cant trust manufactures they like to sandbag.

Here's another thing:
The stock alternator puts out 180 Amperes at 18 volts. This means it puts out 2500 Watts.
This roughly equates 3 Horsepower.
An alternator has a high conversion efficiency, maybe 90 %?
So to put out the 3 HP, it consumes say 3.2 HP.
In other words, puts out 3.2 HP worth of powering this and that electrical components, by reducing the engine's output by 3.2 HP.

Except ..... if you have the alternator management.
Then it doesn't reduce anything, temporarily, while you accelerate or dyno. The alternator management is like a factory underdrive pulley without the downsides.

So then, the cars WITH that option should be rated at 3 HP more. But they don't rate cars individually inside the C63 range, except if they're part of an edition.
What if ALL black series have alternator management?
Then the whole black series is worth the extra 3 HP ...

not too sure I personally like the idea of alternator management. i enjoy having maximum spark at all RPM levels and a 3hp increase is not worth the decrease of power due to lack of spark or misfire causing engine failure.

You can't compare Pferdestaerken stated in German articles with the stated HP in the US. German standard is KW and that should be used as a reference. Besides that,
German/ECE cars have different components which can give them higher KW output. for example the fuel pump, fuel tank, air intake, location of catalytic converters and many other components are different. Mainly because of more strict emission laws in California therefore USA. Usually cars for the US market made in Europe have little less power and the conversion from PS to HP (BHP) isn't helping.

Help your own point by posting what you know to be the correct European KW or PS numbers.
The Watt as a measure of power, and for that matter the KiloWatt as well, are part of the International Measurement System, just like the Pferdestarke and like the Horsepower.
As such, and because they're scientifically established measurement units, there are well known formulae, which allow conversion from one unit to another.

Back to your point regarding differences between EU and US models.
In the past, there have been differences between EU and US models for German cars, not so much for Italian cars.
I am aware of this and this is why you saw in my post me researching the R63 AMG. The source that I've found is Autobild. I would also look at Auto Motor und Sport.
But if you have something more reliable for EU stated power numbers, please, post here the PS and we'll convert them, so see how they line up.
Again, for the R63, this doen't seem to hold water.
And also, the power numbers are not REQUIRED to be different. They CAN be different sometimes.

And you know what? Let's take the power numbers for an AMG model from mercedes.de and mercedes.com and let's convert them, let's see where it stands now. I'm curios to know..

SO, I checked the Mercedes.de C63S sedan
510 PS
The Mercedes USA C63 S sedan
503 HP
510 PS=503 HP

Anyway, the problem was in the past that you have the magazine writers that get the car to review before Mercedes puts it up for sale in US.
These days, these people are entertainers, not engineers. SO they copy-paste the press release into their article.
So the Mercedes press release is in PS, not HP, so they throw it right in there in PS.
So the readers just remember the number, they're not at fault.
One could ask why the person at Mercedes that puts out the press release for US is not paying attention...
But whatever.

The advertised number is certified to SAE J1349 which is close to EEC 80/1269.
The era of under/over rating ended with the recall of the 2000 Mustang Cobra SVT due to untrue horsepower (wasn't cheap) and with the lawsuit over the untrue horsepower rating of the Mazda RX8 in 2006.
Now, to avoid financial unpleasantness, they SAE certify the numbers, since 2007.

As far as the row boxes, no other intake piece is different. I believe they're for fuel vapor emissions.
The power they make is by leaning out the AFR. Especially with aftermarket filters.
As long as they have the same AFR, both cars would make the same power.
The tune of the Cars with ROW is probably different and the injectors are certainly different.

People outside US should not buy the injectors referenced on the forum because their part number is different.