Hi johnnyhughes,

If you do a search on rough or high idle, you will find more than you want to know about it.
My first thought would be to clean the idle control valve. Also worth a search.
Second would be a fuel injection cleaner in a tank of gas and give it a good work-out.
The slight drop when driving could be the AC kicking in at that time. The system is supposed to correct for that, but when a car sits idle (no pun intended), rubber parts dry out and thinks get stuck.

I would change all fluids also and thus make sure all the bases are covered.

Enjoy the car.

Reinhard Kreutzer