88 4.0 Cherokee dies out in higher RPM.

I have a 1988 Jeep Cherokee Pioneer 4.0, 5spd 57K original. I just bought the truck about 7 months ago and have already put 11K on it. Love the truck but am having a problem with it loosing power in 2nd thru 5th gear. It looses power completely or it dies out but then comes back again maybe a second or two later. Like it’s not getting enough fuel or oxygen. It is really annoying because the truck looses power at about 1800 to 2200 rpm’s, never at a specific point. I have changed the Idle Air control valve Clutch assembly (pilot bearing was shot) and gave it a complete tune-up. Checked the voltage on the T.P.S. looks good, exhaust is about a year old. I read through all the problems on the Automotive forum but there are none like this where I could get help. Please, if there is anyone out there that could point me in the right direction I would greatly appreciate it.

You said the TPS is "good", does it happen when you accel to a certian point on the gas pedal. If so it could be your TPS. Other things check your distibutor. Check your stator resistance. A chilton should give you the proper numbers. Do you have an ESS light on?

It does not happen at the same time always. Once and a while she runs fine. But the last time I checked the voltage on the TPS it was O.K. No there are no lights on the dash. I am not sure what the ESS light is? Do you think it might be an oxygen sensor. I am going to pick one up because I heard that it should be replaced @ 60K. If that doesnt work I might just bring it to a local shop to see if they could run a computer diagnostics check to see if there any codes.

You said you did full tune up. Did you change the fuel filter? Dist Cap? Did you check fuel pressure?

Yes I changed the spark plugs, rotor, dist cap, fuel filter, idle air control valve and air filter. I just went to a local shop to get the computer diagnostic check and it didnt come up with any error codes. I am going to put a new oxygen sensor and fuel injection cleaner today. I will take another look at the dist cap also just to make sure everything looks O.K. Lets see what happens. I am going crazy with this, somebody please help!