2000 3.9L issues when cold

I have a 2000 Dakota SLT 4X4 3.9 V6 5 spd. When I rev the engine up when cold the rpms don't come down for a few seconds after I take my foot off of the gas. Also the exhaust note is quite loud until it warms up, I will be driving along and all of a sudden the engine will quieten down and smooth right out. At that point it will also stop revving high when shifting.

I have cleaned the throttle body and checked that the butterfly is not sticking, and have cleaned the IAC motor. There is no engine light.

Lately when I start the truck after it has sat for a while it will run rough or stall if I don't give it gas for a minute or two.

Any advice would be appreciated.

Thanks, Ross