Intake Manifold Question???

Talking to "Jeeptherapy", He mentioned that a newer intake would be a good performance upgrade for my 92 XJ. Can anyone give me an idea what one has cost in your experience and whether a exhaust man. chnage would be good to do at the same time? What kind of performance did you get and did you get an extra mile or two from the fuel?
What years are the good ones to go with?
Thanks

I've got a '92 as well and just did this swap on my 4.0 with 241k miles on it. I was told that adding this Intke mani should give about 40 more hp. Not quite sure how true though. I have noticed a quicker throttle response and better on-highway hill pulling. I got my manifold on a '99 motor I bought. I thought I'd try this swap and keep it until I blew up my orig. motor. I did scrap all the '92 accessory mounts and bought ones for a '99. I had to get a '99 power steering pump and it's mount for as well. The stock exhaust mani works just fine. Take a look at the vacuum routing and sensors on the orig. Mani. and plan ahead. That way the swap is cake. It all fits just fine. One thing, You'll have to get a Serp. belt for a '99 because changing to the newer mount, changes the length of the belt and belt routing. Any other questions PM me!!!! P.S. I got my parts off of Ebay, believe it or not