Well, first, expect that when it is working correctly it will always idle high for a moment and settle. I do not know of any EFI controller that doesn't do that, hot or cold. Basically it's a stepper motor for the IAC and after it fires, it eases it down, some are programmable like my EEC-IV but others just do what the company thinks will work for all.
Honestly its one thing I don't like about EFI, if you want good idle control, most of them don't return to idle like a carb, they ave a little hang time at the bottom
Second, as far as the throttle body and leaning, it really doesn't matter in terms of leaning cylinders nor the TPS and honestly, I think I'd try the secondary TB. No matter which set of blades you open, some cylinders will be leaner than others, the O2 sensor only looks at the combined mess and adjusts all injectors, so no matter where you add air, it's got variance
The thing to remember though is that extra air is only at idle, as soon as the TPS shows a change, it uses a different table and adjusts accordingly, so a second reason it just doesn't matter
Your idea of the second TB being different is correct, the primary TB will have the TPS, remember, a TPS is based on two voltages, idle and wide open, everything in between that is a percentage of change. That's why when you calibrate the TPS it just asks for those two figures. it doesn't care where it is, it just wants to know where closed throttle and open is and then it looks for the difference between those two points.
Therefore, the nice thing about trying the secondary TB is that it will add air without messing up your closed throttle TPS setting and therefore also not require a TPS recalibration with each change.
The MAP is far less critical it just needs manifold vacuum, all it does is judge load after it sees where the TPS is. TPS with no vacuum, means it's time for the engine to really work, more TPS with some vacuum, still in cruise just high RPM, it's an input to allow it to make a decision
Again though, you are trying to make the car do something without understanding the programming (not your fault FAST hasn't really told us, unlike the more advanced controllers) and
without giving it a chance to do its own magic.
Please realize this, change ANYTHING and learning is invalid. This is not a carb, in this case, you get close and it tweaks from there over time and in varying conditions. The ECM is looking for cause and effect with trends, when you change a mechanical or timing adjustment etc, what it learned ca be irrelevant and it needs to start over, or at least re-tweak
I know I am being a broken record, but I am hoping to get you to think differently. I still think like you feel you need to fix something. All you need to do is get it on the road at this point. You still haven't got volume and heat through the exhaust to clean up the mufflers, and you still haven't given it any road time to learn.
We are still at "
get it to run cool and then drive it" the
first bite of the elephant, we haven't got by that yet. I promise, things will get better fast once we can get some road time on it. We may even have you tweak EFI stuff, but even the engine temps will be different soon, so again, any tweaking or learning is useless now.
If I were in the room, I'd say,
stop touching the distributor, stop touching the TBs, and finish the cooling system. If you don't have what you need to do that, take a nap, or come to Disney and drink some whiskey with me until you do have the partsOne last comment on edit - When
coolant temp (temp sensor),
idle vacuum (MAP), and
throttle positions (TPS) are constant and repeatable to the computer
and the car
reaches temp AND the car
experiences normal use, the computer will start learning and adjusting it's tables based on O2 sensor output and the programming you requested at start up.
Until you get those things in italics to be stable and then you actually drive the car, you are chasing your tail. Note the simplicity, stable temp, repeatable idle conditions, and normal use. If you REALLY need to do something, find some belts