1976 Toyota Corolla Engine runs lean at part throttle.

Car runs lean at part throttle when cruising on the highway or accelerating moderately like from a stop or just wanting to speed up a little. Car will surge, run unevenly and even backfire through the carburetor a little but. Engine runs fine at idle and at wide open or almost wide open throttle. Problem started seveal months ago and is getting worse.
I had the carburetor rebuilt a few weeks ago buy a local shop that specializes in carburetors because it was leaking. I replaced the wires, spark plugs, cap & rotor and points but this hasn't solved the problem. I blocked the vacumm to the vacumm advance on the distributor but that didn't make any difference.
So is there an EGR vavle on this car that could be the problem? There is something that looks like an EGR valve in the back but not sure if it one.