Here is the procedure for adjusting the IAC (provided to me by John Young from Vegas:

IAC adjustment procedure

1. Remove air cleaner

2. Plug any vacuum line ports as required

3. With IAC valve connected, ground diagnostic terminal (thatÆs the ALDL connector under the center console, most auto parts stores sell a jumper for GM diagnostic work, that's how you read your flash codes )

4. Turn on ignition, DO NOT START ENGINE. Wait at least 30 sec. (this allows IAC pentle to extend and seat in throttle body)

5. With ignition ON, disconnect IAC valve electrical connector.

6. Remove ground jumper from diagnostic connector (ALDL) and start engine.

7. Remove the plug that covers the idle stop screw (I can't remember if the Holley has one)

8. Adjust the idle stop screw, to obtain 700 RPM (+ or -25) in neutral. 500-550 in drive for automatic.

9. Turn ignition OFF and reconnect IAC valve electrical connector.

10. Unplug any plugged vacuum line ports and reinstall air cleaner.

It seems that I have to go through this procedure several times a year. Three V-6 troopers - Three sets of 1.6 rocker arms installed - one Dyna max muffler and cat. Every mod seems to change the idle somewhat.