I have a basically stock 1991 corvette. After the installation of some hooker 2151 longtubes, my A/F ratio wanders from about 12:1 all the way to 19:1. This is especially bad at low RPM's, less than 2000. It only occurs at low throttle position, if I give it more than about 10% throttle it straightens right out. Ocassionally, it will go so lean that the engine stalls. I have tried increasing the fuel below 1600 RPM's via tunercat with no real results.

I don't have a laptop so I don't have a way to datalog it, but I do have a PLX in car wideband A/F gauge. The PLX wideband utilizes a 5 wire, heated bosch O2 sensor. It also has a narrowband output so you can use it in place of your factory O2 sensor. I suspected the O2 sensor might be the culprit so I re-wired the O2 circuit to use the PLX bosche sensor and it made no difference. The A/F ratio still wanders.

Advice?