[Neil]

A simple check to do for anyone with more than two limbs, unhook your intake tube from your intake manifold. Just inside the throttle body (big hole facing the passenger side of the car)(stated this way because I don't know your skills), There will be two little holes. With the car running, and the symptoms acting up, put your finger over the hole and see if this changes your idle.

One important question I do need answered is, Does the idle drop to the basement from a certain RPM, or does is just sit and bounce between 3 or 4 hundred RPM variance? This would be helpful.