90 4.0, low power

So, I've got my 1990 xj with 315k miles on it. Runs smooth, all plugs nice and tan in color, 125-140psi compression, fuel pressure 31psi with regulator/39psi without, refreshed all grounds and connectors, recent cps, o2 sensor, fuel filter, no cat (not required in WA state after 25 yr old), thrush turbo muffler, and recent tuneup. Only 31x10.50 tires. 3.55 gears. Problem is no power! Feels like I have a 4cyl under the hood! My sons 91 with 33" tires and 3.55 gears will run circles around mine! Ive read all of Cruisers tips and am working my way thru them as time allows, but which ones apply to power output? Until I did a compression test, I thought the engine was just old and worn. It really does run great, just really short of power! HELP!