I have a 2008 cobalt SS/TC and just installed a ZZP fenderwell intake. Took it out for a drive and everything seemed normal, no check engine lights and the idle was fine. Until I did a pull, boost spiked to 20-25 psi like normal and then immediately dropped off to like 5. When I had the stock air box in it would hold boost until I let off the throttle. Thoughts please?

 

Sounds like you went into limp mode ( limited to 5 psi) Do you have CEL now?

 

No I haven’t had a check engine light yet, when I first started it up after installing it the idle was a little rough but it smoothed after letting it run. I put the factory air box back in just to check and see and it held boost at 25 psi just like before.

 

Still check for codes even with no CEL.

Aftermarket intakes will change your airflow calibration. With the ZZP installed, drive around for some time and see what your fuel trims are doing just to be safe here. You may need to inspect your MAP sensor and bypass valve, bypass solenoid operation. The computer should be pissed off it is not achieving it's desired boost, so hopefully you have access to a scanner to see if any codes are pending.

 

I have 08 ss/tc, zzp tune, catless, k&n. I have been running this setup for about 1 year with no problems. Changed the spark plugs Christmas Eve and “raced” it hard last night shut it off for 2 hours got back in and now when wot it builds boost to about 16-20psi then like starts stuttering/ dumping boost. Engine is fine revs fine clean idle

edit: I have a bt code reader, no codes showing