Hello all, just an update. I was able to get the temp up in the garage and got to work. The P1126 CEL that started all of this was for bank 2, so I started there. It took a little longer than I anticipated, so I only got bank 2 fuel injectors replaced. I'll do bank 1 when I get some warm weather again.
Unfortunately, there was no real change to the idle/throttle condition. Upon first start the engine still responds very poorly to throttle input. Backing down the driveway, response improves slightly, but not much. I left the engine top cover off for the first 5 minute drive so I could monitor for leaking fuel at stop signs. With that cover off, I can clearly hear swooshing noises when I crack the throttle, especially on blips. At one point, when I was first pulling away from the driveway, I could even hear a whistling noise, so I'm convinced this must be a vacuum leak. Another run at the intake smoker when the weather gets warmer.
Anyway, in frustration, I took a quick (and annoyingly shaky) video with my phone to listen to in an attempt to locate the noise. It appears to me to be coming from the vicinity of the throttle body. I've decided to upload the video and post a link in this thread in case anyone wanted to take a listen and see if it sparks any thoughts on further troubleshooting.
https://vimeo.com/501941938 (truly sorry for how bad this video is. I might make a more patient attempt soon)
I think I may get a unidirectional microphone I can move around the engine and listen while a buddy hits the throttle as well, to see if i can really narrow it down. I have avoided using the "spray carb cleaner" step the whole time, but I might do that tomorrow in the area where the infamous J-tube connects to the plenum.
So, I guess right now, my question to you folks is, "Do you think the sounds in the video I linked indicate a vacuum leak?" Please feel free to let me know what it could be if it does not sound like a vacuum leak as well. As usual, thank you for your time!