Three weeks ago I dropped my boost back to 16 lbs. Put my 16-19 lbs TT chip in and the car ran fine. then I got a mass air flow code. Car would run fine at one start up then mess up the next time. I put a new maf on today now at hard take off I'm getting what sounds like spark knock or a clattering noise. S-M showing low knock. 1-1.5. thanks for any imput