ISV tech question

I've been having idle problems on and off for 2 years. I had me engine codes scan and the shop said I had an 02 code come up as well as two others. I replaced my 02 sensor last year so they said it was probabbally the ISV. They cleaned it and the car worked fine for 2 days. All of the sudden it stalled out of no where and the idle issuse started up all over again. I bought a used ISV from a friend who said it worked fine. Needless to say the car may actually be worse than before.
Here is the kicker. If I get on the throttle for a while the car will idle fine afterwards. This leads me to believe that it is one of two things. Its either the ISV sticking and it unfreezes after a good jolt or its something else. Before I go out and drom $170 on a third ISV what are your opinions?