Sometimes, at totally random moments anywhere from 40 to 80 MPH, my RPMS drop to idle levels and the neddle 'bounces' from 700 to 1200 a few times but during this time all I am doing is coasting.

I seem to fix it by throwing it into neutral and then back into drive. A few times in rush hour traffic I actually had to stop completely.

At first I ran the supreme gas through it and the problem went away fro 6 months, but it's back again and I've done everything except get it hooked up to a diagnostic.

any ideas about where I should start my search?

 

This may sound stupid but jiggle your airflow sensor. I had a high idle [1800rpm] problem (on warmup) a few months ago. Checking my wiring, jiggled all the sensors and only got a response when the MASensor was jiggled.

What do u have to lose....