99 Mustang 3.8 with irritating problem idle

The car I have is a 1999 Mustang 3.8L. Okay I have had this problem since 30000 miles and the car now has about 115000 miles and nobody can fix it so far. I have noticed that when I drive my car sometimes at idle at a stop light it wants to jump 200-500rpms. This is annoying but not my major concern. The major concern comes from shwne I drive it mostly on the freeway then park it for 15-20 Minutes and come back out and start it up the engine almost wants to stall. This is especially bad when reversing. I also get the rpm surge when I am stuck in traffic for a long time say a wreck on the interstate. I am contemplating buying an ELM5 scanner to help me figure it out. Anyway the things I have done so far is replaced plugs, PCV Valve. Cleaned out throttle body and Idle Air Control. Cleaned MAF Wire very carefully.Checked Throttle Position Setting voltage which was 1.0 a little high. Any ideas on what could cause this and whether I should get the scanner. Thanks all