i have the exact same problem, i have a 98 with 200k, 5spd, 4.0. I just bought it and have added, 2" coil spacers, 32" tires, intake, throttle body spacer, & banks monster exhaust. I also changed the plugs and wires. It Runs great, but in 5th gear it sort of loses power around 60ish and i have to bury the pedal to get it to get back up to speed and if I hit a hill.........forget about it, I have to drop down into 4th. I figured 32" tires with the 4.0 and 5 speed it should be ok, any suggestions?