chevvy

First time posting and looking for some direction on a plan forward - take a seat and grab some popcorn :-)

Here is the history:
Two years ago I purchased a 2002 SLK32 AMG with 62,000 km's so ~ 37,000 miles
Its a Sunday driver so I put ~ 1200 miles on it in the last two seasons.
Decided to add some performance mods to it this last spring (2017)
Here is the list:
ECU upgrade/remapping for the following upgrades:
DCAI
Larger crank pulley -178mm
Larger intake manifolds - new design with two tubes connecting both manifolds
Polished lower Y-pipe to supercharger
Oil catch can
Updated Fuel Filter - Regulator
Fuel pressure gauge to fuel rail
I also installed a set of new plugs and a new IC pump at the same time along with an engine oil change.

By the time the parts arrived and installed it was June so was quite anxious to get my car on the road.
The first drive showed up some problems - on WOT @ ~ 5000 RPM there was some audible detonation which triggered the Service Engine Light.
0300 Random Misfire
0305 Misfire on #5
Fuel pressure at the rail was 58 PSI cold and would go down to 54 PSI after the engine was warmed up.
Talked with the person I purchased my mods from (Mod man) and after some discussion it was determined to install the upgraded SL55 AMG fuel pump to get the desired 58 PSI at the fuel rail.
This also included installing a high flow fuel filter along with an adjustable fuel pressure regulator.

I added these parts and with doing some tweaking with the fuel pressure regulator was able to get the car to run without knocking and setting off the service light.
Fuel pressure at pump running 68 PSI and fuel pressure at the rail running @ 60 PSI was what was used to achieve WOT without setting off codes.

I put ~ 300 miles on the car during all this time of tweaking.
Car sat for a few weeks and decided to take for a trip to work. On the way car received another code - misfire on cylinder 5 - 0305. This was the first time I received a code at an even highway speed - all other times where at WOT.
Car started running very poorly and could not clear the code by shutting off engine (all other times was able to clear the code by shutting of the engine).
Had to park the car to do some investigating.

Pulled #5 plug and it was oil soaked.
Pulled off drivers side intake manifold and oil was pooled on both #5 intake valves. There was an oil film inside the intake manifold but no oil pooled on the other valves.
Again communicated with Mod man and was asked to ensure all passages hooked to catch can where open and clear. This proved all good. At this time I decided to
check the catch can - it had 6 ounces of oil in it. Then checked my oil level - down ~ 1 quart. This motor did not use any oil prior so this was getting me quite very nervous!

My initial thought was that a boost spike blow off one or both of the #5 intake valve guide seals which would explain the oil on top of the valves and the sudden oil consumption. I could not visually confirm as there is not enough room between valve springs to clearly see if the valve seal/seals were unseated.

Did more conversing with Mod man and it was decided to get a cylinder leak down test kit to help trouble shoot/pin point the cause.

I had to order the kit so while waiting I came up with an idea on how to check if the valves seals were the problem.

I made up a cover out of plexiglass with a gasket, along with a tire valve stem installed in the middle of the cover. This cover was place & fastened over the #5 intake port. I manually turned the engine to get the #5 cylinder on the top of the compression stroke. This created the #5 intake port to be a closed chamber - the only physical way air could escape was either though the valve seals or the head gasket. This, with the assumption that the intake valves were fine.
I turned down the pressure on my air compressor to 10 PSI to ensure no overpressure concerns - I could not pressure up the chamber - air escaped immediately. I could not tell for sure where it was escaping so added a light tissue in different areas. The valve seals seemed fine, placed tissue on the #4 intake port and it blew off immediately. My take on this was showing I have a head gasket cracked/broken between #4 & #5 cylinder.

Fast forward a few days - and kit shows up.
Did a cylinder leak down test on all cylinders starting with #5 cylinder with the following results:

Cylinder #5: 75 psi in - maintained 11 psi = ~ 85% leakage. This confirms my initial test results.
Hoping it to be the head gasket between 4 & 5 and not a hole in the piston!

Cylinder #1: 75 psi in - maintained 74 psi = ~ 1% leakage. Awesome result!

Cylinder #4: 75 psi in - stayed at 60 psi for ~ 5 seconds than shot up to 72 psi
Initially ~ 32% leakage than to ~ 4% leakage. My take on this is the cracked head gasket is getting pressured back into place??

Cylinder #3: 75 psi in - maintained to 74 psi = ~ 1% leakage. Awesome result!

Cylinder #6: 75 psi in - maintained 60 psi = ~ 32% leakage. Not good!
This is disturbing as may have some issues with the rings/piston??
Hoping when head is removed will show a problem with the head gasket between 5 & 6 similar to 4 & 5.

Cylinder #2: 75 psi in - maintained 74 psi = ~ 1% leakage. Awesome result…………..but
The bad news on this cylinder was the condition of plug (lack of electrode/insulator) which can’t be good for the cylinder :-(

Cylinder #5: did again with the same results @ 85% leakage.

Cylinder #4: did again with identical results @ 32% then with pressure increasing after several seconds to achieve 4% leakage.

This test was performed with the valve covers removed so could not tell where the air was escaping to for sure so the following day I installed the covers and performed the leak down test on the 4, 5 & 6 cylinders that had the poor results.
All three vented air into the crankcase &/or out the valve cover vents so most likely the head gasket is cracked on both sides of the #5 cylinder. Will confirm once the head gasket is removed.
During the leak down test I was very disturbed to find the #2 spark plug to have the electrode melted off and the insulator gone. This lead me to removing and analyzing all the plugs. Plugs from #1,#4 are white in colour & #2 is melted away. Could not confirm colour from #5 as they are oil soaked. I will assume they would be white as well so those cylinders are running too lean. #3 & #6 spark plugs were a nice light brown colour so appear to be running at a nice fuel/air mixture.

In light of all this my take on the problem are the custom intake manifolds are not allowing an even air distribution to all the cylinders which is causing my situation.

I put this past my Mod man and he stats that would not be possible due to "the manifolds are equally pressurized and thus feed each cylinder equally when the valves open one at a time. The crossover tubes are not there to feed an individual cylinder, they are there to feed the plenums by increasing their volume. The plenums are what feeds the cylinders".

I am looking for some direction on what I need to change to ensure I do not get the same problem when repairs have been completed.

Comments now would be greatly appreciated as I am presently waiting on parts/tools to replace the head gaskets.

Will communicate my findings on the head gaskets to confirm my thoughts with the problem between 4/5 & 5/6 cylinders.

Stay tuned and thanks in advance for any and all ideas to help ensure problem gets resolved/solved.

In signing off, in no way do I intend this to be a finger pointing/negative rant on what I should of or should not of done!
My goal here is to repair my engine problem and ensure it does not come back and bite me in the butt.

Cheers,
Chevvy