G's 84 Runner

Need some help figuring out what my problem could be. I have a 84 runner 146k on the 22r with a weber 38 carb, and an LC header. These are the only engine mods that I have made beside replacing a water pump pulley and mech. fuel pump. It has run like a champ until lately. It has started to choke out in the power range (3-4k) on the tachometer. I have reset the carb and replaced the gaskets, replaced the intake manifold gasket assuming I had a intake leak, but I am still having what seems like a fuel to air mixture problem. I have adjusted the mixture screws many time trying to get the right spot, but I'm not getting it, so I am thinking maybe it is something else. I've been wanting to pop off the head cover and replace the gasket because there is some build up around there. Could this having anything to do with my issue? Should I consider rebuilding soon or will some top end maintenance be the cure? Any suggestions would help.

the_supernerd

I have heard of bad plug wires cutting out under load. Try a full tune-up if you have not done so already. Check the ignition system, it could cause it to cut out. I would think that if you need a rebuild, the engine would be weak throughout the powerband, not just between 3-4k RPMs. How does it run above 4k RPMs? Does it idle well?