I am having a issue with a LS3 installed in a 1957 Chevy. It is using the E67 ECU out of a Trailblazer SS. The previous tuner locked the ECU so I cannot get into this one at all. The car runs rough and throws check engine lights for MAF sensor and occasionally Lean Bank 1 and Lean Bank 2. At the request of the customer we replaced the MAF (card style) with a new ACdelco one. It did not change the situation. What I am noticing on the scanner is that when you start the car the LTFT 1 & 2 is at -17 and stays in the negatives when you drive it. If i unplug the MAF and plug it back in after a few seconds while it is running the LTFT drops to 0 and the car runs better through out. I turn off the car and start it back up and the LTFT drops down to -17 and runs poorly again. If the previous tuner has the fuel system setup really rich in the tune will that make this happen? I am thinking I will need to get another ECU that isnt locked and start over but I want to cross my Ts and dot my Is.
Also, the air intake tube that was on it has a huge vacuum leak. Is it possible it was tuned for that vacuum leak and now that I have replaced the Tube it no longer has that extra air?