1990 Mazda RX7 acceleration problem

I am having a problem while accelerating past 2000 rpm. It seems to only happen after the car has warmed up for a while or while the car is sitting at idle. The car will not rev past 2000rpm, I can then turn the car off and crank it back up, and it lets me rev past 2000rpm for a short time and then back to bogging down at 2000rpm. Please help - I am stumped on this one.