I'm having an idle surge problem with my 89 VW Golf II. It's a 1.8L 8V manual. Car seems to start fine, and seems to idle fine first thing in the morning, but after I put it in gear and start driving, it goes into surging nearly every time I stop. There are times periodically when it doesn't surge when stopped, but very infrequently. The car seems to run down the road fine. I don't notice any surging at speed on the road, or any lack of power, so my guess is that it isn't a plugged fuel filter. It's an American spec car as far as I can tell, as the speedometer is in MPH.

So far I've changed the spark plugs and plug wires. I have a new distributor cap/rotor on order. I just bought the car so I've not had a chance to take a really good look under the hood. Wondering if it's vacuum related. Any ideas on where I should look?