i will start the truck and will idle perfect but when i am driving down the road and i go to slow down and push the clutch in the rpms stay up and do not drop down till i am almost completely stopped. but when they drop down it idles perfect... i have no idea what it could be.. any and all help is greatly appreciated... oh and when i am driving i can let off the gas and it will hold rpms and not slow down with no foot on the gas petal...

 

Clean up the gunk in the throttle body and the IAC valve. Also could be a vacuum leak.

 

Could be a leak somewhere related to the brakes? Boost maybe or even just a bad check valve.