The most noticable mod I made to mine was a complete exhaust. Pacesetter Header, catco high flow catylatic converter, and a Flowmastwer 40 series. This made a huge difference. I think the best way to get more juice out of a 4.2 is to put a 4.0 head on it so you want to look at this before ordering your header. The 4.0 head will increase your compression. Do a little research on this and see what you think, it has been a while since I looked into this and I can't remember all the details. I know you will want to get as much of the wiring as you can along with the,computer, intake, and fuel injection.