My 98 F150 has been having an issue with the rpm dropping to about 400 rpms when I come to a stop and then it recovers back to 600rpms. The truck has 4.6L with about 257000mi on it. I havn't had any engine codes or any other signs of problems the truck runs fine down the road or driving in town.

 

On the top there is a tubular device with an electrical connector on it.
Remove it and spray clean with throttle body cleaner inside to disolve the gum and dirt out.
Make sure the 'pintle' valve moves freely.
Might as well remove the air hose on the throttle body and spray clean the plate and bore area until it's clean while holding it in the open position..
Only problem your having is the IAC is sticking closed upon decelleration then it recovers to slowly.
That's what your cleaning.
Good luck.

 

Thank Bluegrass I will give it a shot!!