OK. So at the end of this summer i'm going to get a 2005 cobalt SS (The supercharged version. NOT the poser SS)

I was wondering what i could do for performance.

I would like to get it up to 275-300 horses, (It runs 205 stock with 12 pounds of boost)............. Those are the stats that chevy gives it, although i was riding in a completely stock 05 ss and we saw it hit 17 pounds at 120 in 4th gear runnin 5 grand...........

I know that if i upgrade the pulley, that it will increase significantly........ but i was wondering if thats hard on the engine, or even the charger

Any suggestions would be great.

Look into the stage 2 kit with the aftercooler. You should also start reading up on meth/alky injection. Exhaust header and full exhaust with high flow cat will help. Check out www.zzperformance.com