Poor idle speed when my engine is warm

I drive a Mitsubishi Eclipse 2000 2.3L.

In the past few days my car has started to idle horribly when the engine warms up. While it is cold, the rpms seem to be normal except for a small fluctuation up and down. However, once the car warms up, it comes short of stalling when it's on neutral or the clutch is depressed. Also, when it's warm there is a delay in the throttle response. However, I have noticed that if I raise the Rpms to 6000 (close to the redline) the idle returns to normal until I start driving again. After I raise the rpms and the idle returns to normal, the throttle response is normal.

Any help would be appreciated Thanks in advance!