if the exhaust system is bigger the exhaust flow is more important. So to compensate the torque loss I need to calibrate fueling to inject more mixture. am I wrong?
Yes. If you are open loop, the MAF tells the ECU how much fuel to inject.
If you are closed loop, the O2 sensors tell the ECU how much fuel to inject.
Either way, any increased flow (from whatever mod) is reflected in the MAF readings, or the O2 sensor readings, respectively.
Please consider reading up on EFI..
as the exhaust gaz is more important, the EGT can be more or less, as the AFR. Right?
I have no idea what you are trying to say here.