Faulty IAC or vacuum leak???
 

I have a 1988 F150 with 302 manual drive. It was surging at highway speeds so I replaced the TPS. Problem with surging went away but truck started to idle very high (2 to 3K). Unplugged the IAC so that it was drivable. Bought new IAC with gasket and installed. Problem with high idle still exists. Do you guys think I got a bad out of stock IAC or do I have a vacuum leak somewhere. If I've got a vacuum leak, I don't know where to start. Any suggestions out there? Thanks.

First step is to check for codes. Run the KOEO tests and CM display.

The simple fact the high idle started after a TPS change makes it very suspect. No sense blindly replacing parts. Start with a code check.

Will do. Thanks