I had the IAC valve replaced a couple thousand miles ago, before I did the TH fix.
This new thing has surfaced only since I did the TH fix. I can drive forever with normal idle behaviour (750RPM) as long as the TH plug is not in place. As soon as the plug goes in, within a few days, my "normal" idle becomes 1200 or so RPMs.
Unlike the high idle I had before replacing the IAC, which came and went, this new behaviour, once it starts, happens all the time....at least until I remove the plug again, and/or reset the computer. If I do that, it's fine for a few days, then starts doing the 1200 RPM idle again.
