1996 Chevy Lumina Engine RPM's

Hello: My vehicle seems to lose power above 65-mph
The tach reads 2100-2300 rpm's. While parked I
cannot rev the engine above 4000-rpm's? Otherwise
it starts/run's smooth. Once, after a 250-mi. Trip, it
became hard to fire-up after being parked for about
10-min. It acted like a stuck/closed throttle-plate?
Thanks Much.