Have a 2005 Cobalt ss/sc that's way down on power. Car ran great for months, came in last week and dynoed 50 wheel horsepower less all of a sudden. Vehicle passed compression, leak-down and injector flow testing. Tune is still where I want it on the timing/af.
So far:
-Exhaust has been upgraded to a lt header and catless 3"
-Spark plugs have been switched for 1 heat range colder plugs
-Supercharger has been verified to produce the same 15.5 psi
-Torque is only off by 10-15 ft. lbs.
-IAT's appear to be within range and heat exchanger is flowing coolant
-Hp curve is significantly affected being 5-19% lower at all rpms