1.5 turns off the seat is a good place to start but, ideally you'll want to hook up a vacuum gauge to the intake (if there's a port available) and shoot for the highest steady vacuum reading at idle.
Clean your plugs up. Hook up vacuum gauge and let the truck warm up. Starting out on the rich side already (we're assuming from plugs) lean it out 'til it drops just below highest steady reading, then richen again until you get high steady read. The idea is to get as lean as possible without suffering any kind of performance problems.
-David
Kustoms-and-Sleds
