What is wrong with my engine Pt.3

1990 F150 5.0 EFI. Engine RPM goes up and makes a hollow sound when depressing or releasing the clutch

[@Needmorehorsepower]

Possible drag from your throughout bearing going bad pushing in on the clutch pushing in on the presure plate and loading the engine a bit when you release it it takes that small presure off the motor just an idea i cant say for sure