i have a 06 cobalt ss, i just put a new clutch in it along with a pacesetter header and a new cat back exhaust and ive had a check engine light on and it said the maf and 02 sensor and map sensor was bad, so i replaced the map, barometric, lower 02,and maf and the car idles smoother now, and will build boost and run great until check engine light kicks on and then it will go into engine power reduce mode and after that if you try to get on it or go above 3grand it will kick into engine power reduce mode and i am out of ideas anyone got any suggestions, i cant even drive the car but a few miles it will usually kick into engine power reduce about five times a day.....

 

Sounds like a cylinder misfire. What CEL code?!

 

last time i had it ran it didnt say anything about a mis fire, but that was before i put the new sensors in the car, the dealer said it could be the air pressure sensor located under the fuel rail.