Cuda not running like it should.

Well weather is getting good, so I thought hey, bring the cuda out. It was running great. Drove it about 40 miles, some on the freeway and the rest in town. Went to Wal-mart, when I started it up and started taking off it seemed to be missing. It is fine as long as you don't try to give it too much gas. It just seems weird that it could be running tops and them run like crap.