Join Date: Dec 2012
Location: Hooterville, MI
First thing I thought of was the learn down feature, but the GMPP removes that, next thing would be vacuum leak, but you should be getting codes for that. I also have the GMPP but had it installed before the connector had been developed, and I've always wondered if crimping affects boost over the long haul. Then again, it's been so long since I've floored the pedal that I don't even know what it reads now. Good luck on figuring it out.