The pursuit has begun, I ordered a 4.0 TB for my old / new to me 91 YJ today. I will install a K&N filter in the factory box to compliment it. I'm anxious to see what the results will be, the 33 inch tires have turned the 5 speed tranny into a 3 speed, hopefully the driving experience will improve some !!!!!!!!! ( 4.88 gears are coming soon ). I have many wanted upgrades, but first must perform some basic needs maintenance. The old YJ has been neglected and mostly sitting in a barn for a while and needs a little TLC to get everything working properly again, just the clean up has been a huge job, bird nest in the dash, rat nest in the air box, unplug and clean all electrical connections and reconnect etc. I have gotten a lot of good info from this sight and will continue to do so, thanks for everyones help.