I have a car with a scrambled big name tune, for what appears to be stock MAF/Fueling car. Fuel trims are right on with the tuned ECU, but my stock 551A makes idle misfire, and fuel trims max out ++. Can anyone figure out what I am missing here? I'm pretty sure it's just an off the shelf stage 2 file, nothing custom... The maps that I see in the scrambled file for MAF and fuel scaling seem correct.

8D0907551A

Car is a 2000, has stock sized Bosch maf.
I've tried tunes I've used on other Bosch cars and just started from scratch with a M-Box with MLHFM, KFKHFM, and MLOFS  transferred over......all act the same.

Pulled the MAF and found this....I hate people.

Flashed 3 different ECUs with the ori 551A file. 1 M-box, 1 L-box, and 1 was 3B0 907 551CG that I run with an m-box tune in my 01. All 3 ran like shit and trimmed to full rich. the CG threw a fault for ECT P1621, but showed correct temp. Flashed the stock file over the APR tuned ecu that came out of the car (that was physically an L-box) and it runs perfectly.

Then I put the 551CG in a bone stock A-Box car, and it ran fine.

I'm thinking the car may have a grounding issue and different hardware versions that should work fine may have different ground or 5V connections internally that makes the original ECU work fine? No idea. Flashed all ecus with the same eeprom as well.

The car did kill and ecu a year ago, when this A-box flashed L-box was installed...