Bank1 fuel trims max out possitive, bank2 at near 0????????

CTS-V 04, 408ci motor, heads, cam, yada yada. Short story. Bank 1 fuel trims go to max + 25% on LTFTs, short terms stay pegged at 33%. Bank2 trims stabilize near 0. O2 function looks normal. Compression ok. New plugs.. Everytime I have ever seen this, it has been o2 connectors switched bank to bank. Owner has checked them and says they are ok. Once PCM gives up on closed loop control, car runs like crap. I am suspicious of fuel injectors as they are some brand that the owner purchased that I have not heard of before. I doubt anything is wrong in the tune file to cause this massive bank to bank discrepancy. Even when locked in open loop and fuel is dialed in with a wide band (after x-pipe) it runs poorly. I have not been able to swap wide band into each bank to verify one bank is lean. Maybe I missed something in this file.....Do not beat me up too bad, it was whipped together to just get the car to run. Im not going to invest too much time into a tune file for something I believe to have a mechanical problem. I do have a set of injectors out of a GT500 I am going to let the customer try also.

Please let me know if anyone sees anything strange. If anyone has flow rates for the 47# (at 40psi) injectors from a GT500 let me know. I can write him a file to try once he swaps them.

THank you
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It would be a physical (mechanical/electrical) problem.

Does bank 1 have an air leak...?

Are any cylinders on bank 1 misfiring (which causes O2 to see excess oxygen since it did not burn with the fuel)...?

Are bank 1 injectors not firing...?

All cylinders appear to be firing. No external signs of vacuum leak....Not disregarding, head gasket leak however. Engine made decent power. 560rwhp, 408, with Trick Flow heads, edlebrock intake, unknown cam.

Try swapping the O2's bank-to-bank.


Then try swapping the connectors/harnesses bank-to-bank.

In many cases you can't assume the customer's story, either he got it wrong, or the people who did it for him got it wrong.

Exactly what I believe.....However convincing the customer of that, and more over his "friends" is much harder. Some people believe the mysterious "tuning" should be able to fix anything. I try and help them as much as I can without taking too much of my time, and without blowing them off so that they get mad.

I had a similar issue with a car that came in a couple of months ago. Turned out the "mechanic" who built it hadn't done the earth bolt up on the back of the head. After a different call out I had last week where a simple fuse was missing in action, I now start diagnosing from the beginning, no matter what the customer has said he has checked.