Doesn't change much at all. Just gives you better throttle response and a nicer sound.

 

If I had to do these modifications say one at a time which would be the best to do first as far as getting better speed, performance, horsepower?

 

The best way to get started is by going with a cai and then moving to the exhaust. You want your engine to breath better, and that's the easiest way to do that. After that, I would check out what www.wot-tech.com has to offer for your 3500.