96 cherokee 4x4 5spd 6cyl. 164,000 miles. Engine starts ok. Low speed not too bad. The faster I try to go the worse it gets. In 5th gear top speed is 54mph and getting slower. Even minor hills are an issue. I step on the pedal even a little bit and it just bogs down. This has been going on for the last 2 months and is getting progressively worse.
I have changed plugs,wires,cap,fuel filter, air filter, tps,fuel pump, muffler, there is no back fire or back spitting. Out of the catalytic converter at idle seems to be plenty of air flow. I even have a leak from the exhaust manifold to the pipe. So no back pressure issues.
Thankyou for any advice.

 

Check the cat anyway. '96 had so many problems with them that there's a lifetime replacement TSB. If you know how to use a vacuum gauge, that's a good way to check.

Have you checked Cylinder compression? Fuel pressure? Checked the TPS through it's range of operation?

 

Check all your wires from the battery terminals. Clean all your grounds. Had the same issue and switched to 0 gauge. Solved all my problems