So I sold my 1976 International Scout and am the proud owner of a 2004 Rubicon TJ with 5 speed manual and 51,000 miles. It’s in great shape with a 3 inch lift and the Banks Power System. It seemed a little sluggish on the test ride, I guess I was expecting a little more power out of it since that Banks System supposedly adds 29 HP to the motor with a header and free flowing exhaust etc. I bought and installed a new serpentine belt and a new set of plugs. The kid at Napa sold me Autolite APP 985 plugs. The gap was preset at .9mm Which is .035 inches Which I thought was correct. It also had a cold air intake with a K&N type air filter. The old plugs were original I’m sure as they were worn but They all were slightly fouled and the gap was around .065 Due to wear. The Pics are of one of the old plugs and one side is nice and tan but the other side is slightly fouled and all the plugs were similar. The air filter was filthy and had absolutely no oil on it. Just prior to tuning it up I had a check engine light and the code showed a bad TPS (throttle position sensor). Welcome to the new age as my Scouts TPS was my heel LOL. I thought I would tune it up and see if the code was caused by old plugs or dirty air filter. I installed the new plugs and cleaned the air filter and Wow! Big difference. A lot more power and it ran nicely for about 5 miles then it developed a sudden miss and loss of power. I thought maybe the TPS was to blame so I bought and installed a Mopar TPS but it’s still missing and the check engine light came back on. I have to go out of town for a few days but I guess I’ll pull the plugs and check them and then limp down to the auto parts store and have them check the code. After looking at some old posts, the gap went up to .04 inches on the motors with the electronic ignition rail which I have. I don’t think that amount of gap error would cause the misfire I’m having but I guess I’ll reset the gap to .04 and see if that helps.