Bad fuel pump would be my first thought, only because it's happening at what sounds to be like the same RPM.
If that's not it, I'd check your fuel filter. I like to have a glass inline filter right ahead of the carb specifically to diagnose these kinds of problems. If the filter is empty and it runs like crap, you know the problem is the pump or a blocked line. If the filter is full and runs like crap, you know it's the carb or the electrical system.
Which brings me to my last point: an old guy once told me that 90-percent of all fuel problems are electrical, and I have yet to prove him wrong.
coil, cap, condenser, rotor, points, plugs, bad wires. Check all those things.
That would have actually been my first suggestion, except it sounds like your problem is occurring at specific RPM, and that wouldn't be electrical.
-Brad
Last edited by Brad54; 05/31/2011 6:04 AM.
