Thanks for the additional information, and the detailed post!
While you have things apart, a little carb cleaner on a rag and/or q-tip will make short work of any varnish in the throttle body bore and iac passages.
Do NOT spray carb cleaner willy nilly around the throttle plate!
You will wash out the lubricant in the throttle shaft bore and will probably replace it with gritty goo, leading to wear and boost leaks out past the seals. Just use blue paper shop towels and some patience, and it'll come out clean with minimal effort.
Re-setting the tps can be a chore, but one of the easiest/most accurate ways to dial this parameter in is to use voltage "seen" at the ecu with a closed throttle. It should read .5v, +/- .02v
It's worth noting that the actual position of the throttle plate will impact these numbers, so it's best to be sure you're not chasing a "tampered" factory adjustment.
For example, the closed throttle switch can hang things open when it's mis-adjusted, and the t-cable needs to have some slack before setting the tps.
As a "general" rule the tps should be ~approximately~ in the center of it's range when the throttle stop/closed idle switch are correctly positioned.
If you're still running the iac, you know that everything's golden when the tps reads .5v, and the iac shows a few counts on an idling warm motor with no loads (lights/climate control/etc off) Add a load, (like turn the steering wheel), and watch for an increase in the iac count. Try again with an electrical load like the lights and heater fan, and it should do the same.
If you delete the iac, set your idle (via the biss) to ~850rpm, with a hotel load or two on. (lights and maybe the heater fan)
This will ensure the alternator is spinning fast enough to make sufficient voltage so as to not strain the voltage regulator. It works hard enough as it is, and an idle speed under 750 will shorten it's service life significantly
If you;re running a turbo timer and have deleted your iac, bump the idle speed up to at least 900rpm. The radiator cooling fans will often cycle on the timer, and that will seriously stress the alternator. (it's actually a worst case scenerio. as the alty tries to put out more juice, it'll load the motor down, and as the rpm sags, it'll load it more, dropping the rpm further.
... and at that lower rpm, not much coolant/oil is being circulated through the engine ...
For what it's worth, I like to use metal for making the fiav block off plate.
Doesn't have to be anything elaborate, a piece of thin aluminum works fine and is easily cut/formed/drilled with hand tools.
Might save you some head scratching when a back fire takes out the playing card/cereal box/gasket material and now you're idling at 2500rpm.