get rid of the aftermarket MAF sensor... bad bad bad.. Aftermarket MAF sensors do not report true, correct information to the pcm... aftermarket MAF sensor calibrations fool the pcm into thinking the engine is running leaner than it really is, so when trying to tune it and adjust the fueling correctly, it will never really be right/correct, because that aftermarket MAF sensor is not reporting true/accurate info to begin with... Plus, they usually cause idle and driveability issues.. once you put your stock GM MAF sensor back on, I'm sure you'll notice it idles and drives much smoother...
Plus, the stock GM MAF sensors are good for 550/600+ hp anyway, so there is no reason to change it... So put the stock GM MAF sensor back on... If you don't have it anymore, then get one...