u/Frequent-Meeting-459

I just bought a 1992 C4 LT1 6 speed and while driving on the highway I noticed the car wouldn’t really slow down when I let off the gas. After I got off the highway I realized it was idling around 2500-3000 RPM in neutral.

Throttle plate looks closed and the service engine light came on. I found one cracked/disconnected rubber vacuum hose/elbow and taped it back together temporarily but it’s still idling high. The RPM kind of dips from 3000 to 2500 and back up again.

Does anybody know what this might be?