There is still a difference. As you saw, mine will slow down at 1500 RPM for a tick. It's not a situation where it hangs and it's for a fraction of a second. The falling of RPM simply slows down as it approaches 1500 RPM, and then it falls back to idle. This was where I was thinking others could offer advice about how their particular cars act, as not every car will fall to idle as mine does (or yours does). The car wanting to stall when cold is still problematic. Perhaps JRcihker has further info or you can revisit his old posts about checking the IAC wiring to ensure it's doing what it should. I'd be going off the cue that the IAC doesnt work when cold. Once that's sorted out, I'd worry about the hang (because fixing the primary issue will likely fix the secondary [hang]). Good luck.