2000 Cavalier Upgrades

I own a 2000 cavalier 2.2l single cam and was wondering if anyone knows of cheap performance upgrades to give it more spunk. I already put in a K&N high flow filter. It didn't do much noticable difference but still worth not having to change the filter, and fuel economy increase. Anyway, I don't make a lot of money so I need cheaper ways of increasing power and making it sound cool without turning it into a lawnmower on wheels.