Okay, I put a new fuel regulator bladder in last year when suddenly I had a hard start and fuel in my vacuum lines. I strung new vacuum lines throughout the engine and replaced my plenum and runner gaskets, and the throttle body gasket. Fuel pressure is normal at about 37-38 PSI and I can't hear any vacuum leaks.... WHISKEY TANGO FOXTROT OVER?!?!?!

Since vacuum leaks aren't always audible I'd spray some carb cleaner of the engine just to be safe, vacuum leaks can cause some funky stuff. Otherwise check your idle air control passage/wiring.

What do you consider a 'high idle'? What was it idling at before? Hot, cold, etc?

Still haven't figured it out. Starting to suspect my IAC. But it used to idle at 650-700 now it's up around 1500.

I replaced my IAC, and it cured it. It was an educated guess.

Well I got a scan tool from a guy at work and I have response from my IAC, MAP, and TPS which are all within range. Now the idle on the scanner said it was 1000-1100 (cold) and my RPM gauge said it was closer to 1500-2000. The desired idle (according to scanner) was 3350. Any ideas?

Did you let it warm? I'd be curious to see what your scan tool reads after the engine is warm, and what your own tach reads. A cold engine will run high. My TBI runs about 1500 when cold. (I'm guessing). After the engine is warm, it settles back down to around 700 according to my tach.

My 1992 RS 25th Annv. did that too when she was cold. I never had that issue with the TPI though. I'm moving her out of storage this week, that should warm her up and I'll see what happens.