So if you stop on a hill, press the clutch, and allow the car to start rolling, at 3-4 mph this surging will begin? This sounds like easily repeatable behavior. If so you can watch logs to see what's changing. Timing usually affects idle speed right away but IAC action is a little slower. If you're getting a large increase or decrease in timing when surging starts then you can try to hunt down a table or constant that's responsible. Same with IAC changes.