Has anyone had any experience with a Jet Performance module? Stage 1 or Stage 2, I just wanna know if anyone has actually got any noticeable power with these? I have a 98 4.0 auto. I plan on buying one of the power pack sets from I think 4wd.com and it comes with exhaust, intake, and a few other things. If anyone has had any experience with these, I'd greatly appreciate your input!!!!

They are a bit pricey IMO for what you get. I got significan performance gains for less than half that price, just by installing upgraded fuel injectors.
I'd stay away from the "stage 2". The long term cost would kill your wallet considering it requires the use of 91 octain fuel, 180 degree t-stat and free flowing exhaust.