Where to start... I have a New (400mile) 06 5.3 Truck with 4L60E in a restored 69 Firebird. I am to the point of hating the car...I've been dicking with this freaking tune for years...no I'm not an idiot, but no matter what I do, I can't get rid of the ridiculous idle issue. I've tuned SD=perfect except for idle area. I've tuned MAF=perfect except for idle. I've tried every idle procedure on this site. I've tried removing over/underspeed spark. I've put idle into open loop. I've followed the 'advanced guide to tuning GM'. If I combine MAF and SD it runs like shit. As long as I'm cruising or driving it's great. If I coast it either goes into 'cruise' mode, or almost 'dies' (scary) while still rolling 15mph around a corner. I'm at a loss....someone please look!!
BTW--I'm in Germany, not too many tuners for GM over here, unless I drive 6hrs.