Help me find out what is wrong with my 1989 GMC jimmy please.?

[alodiwolfsong]

When it gets under a load or pull as in picking up speed or going uphill it feels like it is missing. I have put in new plugs, wires, distributor cap, rotor bug, fuel pump and EGR valve. I'm about at my wit's end! Could it be the catylytic convertor is plugged? HELP! Oh, It has the throttle body carb and is a 4 wheel drive with the big 6 cyclinder engine. It does run rough all the time, but when you get a load put on it it tends to heat up a little bit. I cannot afford to leave it at a shop and have them fix it THEN tell me what it cost.
Yes, I changed all filters.

 

[randyrandola]

Possible that it is the cat. Save dollars and punch it out b4 replacing it.
Timing may be out. Check this first. And not just at one mechanic.
Did you replace the fuel filter(s)? Air filter?
Just for an experiment, get some carb cleaner and while the engine s running, spray it around the intake manifold, base of the carb, any hoses you may see. If the engine starts to die or rev up, then you have a vacuum leak.

Good luck.