My 1994 had the EXACT same problem. Not always, but sometimes, at idle the engine would simply die. I checked all the same stuff as you, to no avail. Yes I tries synching the throttle cables, too.
I finally determined that the default throttle angle was set just a frog's hair too much in the closed position such that the time lag between between (a) the engine controller computer recognizing that the idle speed was too low and (b) the response time of the IAC was *too long*. As such, the IAC was a millisecond too slow to respond. Hence the stall. Now that I think about it, it was more prone to do this in warmer weather, AFTER the engine had warmed up.
Each throttle body has a teeny tiny set screw down near the bottom edge. This set screw is used to set the default "closed" position of the throttle body. What I did was to turn the set screw on each throttle body 1/4 to 1/2 of a turn. AND IT WORKED! My idle speed did NOT increase, I never had a problem with engine surges at idle, and THE ENGINE NEVER STALLED AGAIN!
At first I thought maybe only one side was "too closed", so I first tried the set screw on the passenger side throttle body. I opened its set screw 1/2 of a turn. This helped somewhat, but it still stalled, albeit not so often. When I did the same to the driver's side throttle body, the problem was simply gone!
Good luck; I hope this helps.