No power

[medic06]

Have a 2001 TJ 4.0 liter 5 speed. For the last month or so I have no power on the highway. Nothing has changed in the last 3 years. Just routine maintenance. Oil changes and plugs replaced. But it's a 4 inch lift with 3.73 gears running 33x12.50 MTZ tires. I know I'm lean on gearing but I've never had trouble in the past. Here recently I can't even hit 2 grand in rpms on the highway. No knocking clutch ain't slipping. Any ideas?

 

[JPNinPA]

I run 33x1050 on 2.5 in lift manual and run 2100 rpm at 70 mph in 6th gear. Rears are 3.73 but the transmission gearing is different than yours.

Clean your TB and IAC.
Clean battery terminals and grounds to body and engine.
Verify low ohmic contact and resistance if the wires.
Is your air cleaner in good shape?
Run some injector cleaner.
Sea foam or water treatment to break carbon buildup from the valves.
Any exhaust or vacuum leaks?
O2 sensors performing?
Cat converter clogged or media gone?
Any issues with u joints?
Temp up at 210 within 2 miles?
Clutch fan operating ok? Not stuck on??
Brake hung up?
What brand and model plugs? Gapping? Alignment? Tire pressure?