I have been searching fo the past week or two, trying to come up with a definitive answer on what to do. And I still don't know!! I have a 07 Cobalt SS S/C with Injen CAI, Ingalls ETD, ZZP Header and Catted Downpipe and GMPP Exhaust. I was looking at buying the Cobalt-Addiction Stage 4 kit, but i don't want to get something that going to blow my engine. My question is what is the most i can do(Pulley Size, Injectors, etc, etc...) with the stock internals to get the most hp/tq. and without changing the blower. This is also my daily driver so has to be very reliable!!

 

Get the GM stage two and throw on a 2.9" pulley. It won't give you the most hp/tq, but it is a pretty safe way to go.

 

If I bought the stage2 kit and a smaller pulley (ex:2.85") would everything fit fine and would i need to reflash?

 

you're starting to push the max of the injectors on the stage 2 tune, but some people are still even running 2.8" pullies. sooooo, the answer would be no, but you might want to think about getting an aftermarket tune to be safer.

 

I guess what i need to know is what my limits are...
Could I run the CA Stage 3 kit + Professional Tune? or instead of the kit should i buy everything seperately then have it tuned?

 

The 2.8 Pulley is either maxing out 42# injectors or close enough it's scary, I would never run a 2.7 pulley on 42# injectors.. 2.8 is also about the smallest pulley you would want to run without quite a few cooling mods.

For reliability GM Stage 2 is your way to go, even if you *do* have a problem it's still under warrenty. The max you can get out of the motor and stay fairly reliable is probably somewhere in the range of 2.8 pulley, 60# injectors with harness, GM Stage 2 belt, 1 step colder plugs, and custom tune. Cooling mods on top of those can only help.