So what's going on with this thing now?

Is your Fast idle valve screw tightened or do you have one?

What he's saying with the brake cleaner is to:

1.crank it up
2. Spray some brake cleaner/throttle cleaner on the intake gasket, throttle body gasket area. And see if the idle goes to normal if it does then whichever gasket is bad or something else in that area has a vacuum leak.
Actually had to do it today on a V6 intake at work. Had a fluctuating idle so I had to take the intake back off and clean the gaskets. Put it back together and was fine after that.