So I finally got around to doing a full bore tune-up on my '01 w/ a 3.9. NGK IX Plugs, Borg Cap, Button, MSD 8mm Wires, new IAC Valve, TB Gasket, Valve Cover Gaskets, painted the valve covers Hemi Orange for that extra 20HP, the standard stuff. With the old it was idling at around 525-560rpm. With the new stuff it holds at 1125-1270 for about 90 secs then drops to 900-ish. If it's warm out(80*+ F) it'll actually hold at around 1300 revs. It wouldn't bother me if it wasn't for fuel consumption w/ gas at $3.12. Old setup was:

Plugs: Champiom 4071 "Truck Plugs"
Wires: Carquest 7mm "Restrictive" wires
Cap + Button: MasterPro
IAC: MasterPro

Any ideas to bring it back to normal?

 

No codes? Was it doing this before you changed the IAC?

How's the TPS? Could also be a vacuum leak.

Moved to correct forum.

 

Only code is a the cooling fan resistor but even that tests fine. The vacuum system is fine. And it was the usual crapout IAC no-idle issue before it was changed. It's not laggy coming down after brapping the throttle but the best way I can compare it to is the old thermal chokes. It's pretty much the same symptoms.