Why is my Toyota Corolla bogging down?

I have an ‘85 Corolla Sedan (4-spd automatic, 4A-C engine w/ carb and distributor) that seems to bog at 2000RPM if I give it too much gas.
It’s only at 2000RPM, and the wider the throttle is open, the worse it is. At light-throttle it won’t do this (or climb a hill; the 4A-C isn’t a powerful engine) and if it gets to/past 2100RPM (or drops below 1900) it acts normally, but if the gas pedal is more than ¼ of the way down then as soon as it hits 2000 it loses power and if the gas pedal is more than halfway down it will actually try to stall.
The plugs are new, the carb has been sprayed down with carb cleaner, and I ran a bottle of fuel system cleaner through it. I’m at a loss!
Why is it doing this? What can I do to correct the problem?