Could anyone please give me some advice on anything that could be done to pep up what little life there is my 4.0L engine. I have priced some cat back systems, but I am not sure if that is all I want done. Any assistance would be of great help. All I am looking for is more power and better mileage. Ok, I could sacrifice the mileage part if need be.

What year truck doyou have? Depending on what year truck it is there are going to be some parts that will work and others that won't.

It is a 98 4x extended cab.

Well, you could try a KKM filter kit, a Vanir 63mm TB, and the cat-back. You should get good results from a single 2 1/2" pipe and muffler after the stock cats with mild bolt-ons...

I put a cat back on my 97 4.0 and noticed an immediate difference. I went and got a 40 series Flowmaster muffler with delta Flow 2/5" in/out. Than just went down to my local Meineke and had them run 2.5" stainless pipe from the convertor back running all the pipe in the stock location. Total bill was like $75 for the muffler and $101 for the pipe and the install. All in all it cost me a good deal less than $200 and there was a deffinate increase in power from the very first time I pulled out of the parking lot. Deffinately a good investment in my book. I also just recently purchase the K&N FIPK. I'm not positive but I think this will work al the way up to the 00 truck but I could be wrong. This was another nice addittion and because I got in on a group deal only cost me $135.

I recently learned the 95-97 FIPK's will not fit the 98+'s. I did hear however that the 98+ kit is coming out sometime around this September(?). I sure hope K&N sticks to their guns on this one; I and many others have been waiting a long time for this kit which I feel is long overdue.