Congrats on your purchase, good choice. I have a 93 Navajo LX. For more power the first thing you should do is let the 4.0 breathe a little better by way of a KKM air filter or K&N, do a search on this site for "AIRBOX MODIFICATIONS" it should tell you everything you need to know about gaining more air. I personally bought the KKM set up for about 90 bucks, best mod for your money. Next mod should be a better release for the extra air consumed, EXHAUST!
again do a search and you'll find different opinions on what's the best for your likings.
I personally bought the BORLA cat-back, it's very expensive but argueably the best you can buy. You'll not convince me other wise, it's top grade stainless steel and it will last forever, I live about 50 feet from saltwater so I also need(I mean WANTED) it, It's somewhat loud under acceleration but sounds great. For further mods keep coming back here and you'll learn about HEADERS, MAFS, CHIPS, THROTTLE BODIES, SUPERCHARGERS, Different gears, etc. My wallet just emptied thinking about all the mods that can be done to the explorer/Navajo. Have fun and enjoy!
Dan
[This message has been edited by Trane (edited 03-13-2000).]