I have a 1994 GMC Sierra 4x4 Z71 350 5.7
i been having some major issues with power loss in the truck. I can barely get up hills with and the engine bogs down and slows down and if am goin down he highway i could be goin 140km to get a run off for the hill and the truck will bog down and slow to 90km or less then its hard gettin it back up to speed again. The truck has new idle air, new distrubutor cap, brand new NGK silcone wires, NGK iridum G-force spark plugs. New temp sensor, tried 5 different MAP sensors on it, cleaned the fuel regulator and injectors.
am not to sure if its the motor causing the trouble or could it be an issue with the transmission in the torque converter or solenoids. I just could use a hand steering in the right direction wthout wastin money on trial and error on a bunch of parts. Lol the truck also will shut off sometimes if u give it a jolt of gas.

Have you checked exhaust back pressure?

Try this....from a dead stop......safely accelerate, as fast as possible......does the engine top out at 3K rpms, bog down, and not shift?

Then come to a stop....now lightly accelerate.......does the vehicle shift and slowly get up to speed?

If yes to both, a back pressure test will probably show a restricted exhaust, usually the catalytic converter.....