Mighty max carb issues

I have a 1989 mighty max that is giving me fits. It has the 2.0 engine, 2 barrel carb. It runs fine until I crowd it to much or run it up over 3000 rpm or so then it acts like the fuel just shuts off, but it's not because at that point there is a lot of black smoke coming out of the exhaust. Hard to get it up to 65 mph. Any ideas?