Hey i put a injen cold air intake on and the straight racing pipe on jul 31st now when u 1st start the car it turns right off only when it has set for a few 5 or more hours , the check engine came on and I reset the ecu and it came back on I think because of the straight racing pipe, and when u shift from park to drive the car rocks back and forth is this normal, it wasn't doing it before the mods help me out

 

this may seem too obvious, but did you recheck all of the sensors, ie is the MAF damaged and did you check to see if you plugged in the other sensor? (can't think of the name). If not it is probably the straight pipe. Good luck