I have a 2005 cobalt ss/sc. I bought the GM stage 1 upgrade for it, then later was looking into buying stage 2. I decided to look around online for a smaller sc pulley for the car to get more horsepower out of it then the one GM offered. I went with a 2.6 inch pulley instead of the GM stage 2 which i believe is 3.25 inch. It was running like a complete beast for awhile, still does but in the higher RPMS it like chugs, or hesitates and sometimes almost feels like the belt is slipping. I had the Belt replaced, now i am getting a feeling that it is starving for fuel, anyone have any idea? maybe i just need another ECU upgrade?