I was having a stumbling problem with my car. It was even worse after I put in my cam (Hotcam). I tried replacing all sorts of sensors, knock module, its a new opti, did coil, plugs, wires, and my next step was to replace the remainder of sensors. I cleaned my MAF meter today with electic parts cleaner and a Q-tip. The stumble is completely gone. I am excited! Car is going on the dyno on monday. Hopefully I can get some power out of it. Good luck.