The symptom I had with a bad throttle position sensor was noticable during gear change. With a warm engine, when changing gears the RPM's would fall very slowly from 4000 to 2500 RPM or so. A new TPS solved this.
I also have a problem similar to what you describe, although not exactly the same. When fully warmed, if the car is shut down and started after a short while it tends to die unless a very slight amount of throttle is applied to get the idle up. This only happens on warm days, say 80 degrees on up. I haven't had the time to track this down yet.
You may want to try the throttle position sensor (switch) first, as it is relatively inexpensive, about $25 I think and easy to replace yourself.
Btw, where are you located?