Last year I had a local gentleman show up with a 2008 Solstice 2.0 Turbo and he wanted me to check the state of his tune. He had installed a K&N filter, cat-back exhaust, and had GM flash the Performance Parts 290hp calibration to his ECM. We went on a test drive and everything the scan data showed looked great - no problems.
This winter he installed a bigger turbo, bigger intercooler, phenolic spacers on the intake manifold, and a high-flow cat. Now his car is hesitating (running lean) during moderate part throttle acceleration (no boost), and the STFT is maxing out at +30% during these periods to try to compensate. At full throttle, there is no problem. At light throttle, fuel trims aren't maxing out but sometimes we are seeing them also drop to -30% during some throttle positions (usually while decelerating).
When the car showed up here today, it had a P0300 misfire code as well as a slow response code for B1S1 o2 sensor stored in memory. The way the car is running, I can see why these codes would set. But with only having 14k miles on it, I don't see how the o2 sensor could have gone bad already.
Anyway, HP Tuners does support this calibration but only gives us limited parameters to adjust. I can adjust the MAF calibration table but I don't see anything in there that would allow me to adjust VE. Does anyone know if these ECMs use dynamic airflow calculations and/or VE tables? Basically what I'm asking is will adjusting only the MAF calibration table allow me to fix this fuel issue?
Has anyone else run into a similar problem before? If so, what did you do to correct the issue?