If you want 15hp maybe cold air intake and exhaust can get you on your way. Also, a shift improver kit may help the car
feel quicker. As Koots said though, it sounds like something is wrong with your engine. Aleros tend to be pretty peppy. Even the four cylinder versions.
https://sites.google.com/site/alerom...e/transmission
In the link it talks a bit about the shift kit.