Mc81b

I would like to enquire if it's normal for your c63 to have the ECL on with modified exhaust and for those exhaust without valves, too much power is lost on the front end especially from standstill?
Any good solution to rectify this issues?

INS1GNIA

What do you considered a "modified exhaust"? I have my secondary cats removed, repalced w/straights and I have no power loss or errors. You should not get any ECL warnings as long as you don't mess with the primary o2 sensor.

Mc81b

I had the cats mid pipe down pipe all replaced with car graphics and the muffler to akrapovic..

abcut973

Right if you don't mess up with your O2 sensors you shouldn't get a CEL.
Now looks like you replaced your OEM by catless cargraphic headers. You should get a tune to disable the O2 not readiness.

Mc81b

And may i safely ask which tune will be good for that?
As long as it does not goes back to MB agent it should be fine as the mechanic claims that the servicing will reset almost every settings..

INS1GNIA

Any tune will work, just explain to the tuner what you have done and they will modify it to your needs. Eurocharge is a good place to start as well/

Servicing will not reset the tune.

avery.whss

Just ask the tuner to disable the O2 sensors and no more CEL

abcut973

^^ Right to all above.
Also if your service requires a ECU reset it will wipe your tune. But generally basic services do not require that unless there is a specific bulletin.