I have a 1992 ranger 2.3L 2wd I got the truck a few weeks ago drove home fine. Installed a new exhaust manifold due to the old one being cracked. After install truck idles fine cold but once warmed up idle surges. Truck will drive fine at low rpm’s but any load or heavy acceleration the truck acts like it dies looses all throttle then it comes back does it until I let off the gas. No CEL when idling but it does come on when I drive but no codes when checked. New parts are O2, MAF, ICM, Coil packs, Plugs and wires, and fuel filter. Some was replaced before me but all very recent fuel pump was changed 3 months ago. Has no cat and after market muffle.

 

Welcome to the forum

How bad was the exhaust manifold cracked?
Could the Cat converter or muffler be clogged, and now with no exhaust leak, the pressure is backing up in exhaust preventing new/air fuel mix from coming in
Test with Vacuum gauge
Or pull out the new O2 sensor(add exhaust leak again) and go for a drive, see if higher RPMs are working again

 

decent size crack but there is no cat anymore it’s been cut out and new after market exhaust so from manifold to muffler is all new