Robert's description is correct. I'd like to ad that a particular driving style seems to exacerbate the problem. If you're a driver that is on and off the throttle (apparently I am) as opposed to maintain a constant pressure and your AFM is not in tip-top shape it will show up. The van will sputter and stall and sometimes you can pop-start it as you're moving, other times it'll start right up after you pull onto the shoulder. Its actually the computer doing it. It gets a signal that the van is getting way too much air and cuts the fuel supply completely. The $300 factory harness is just 2 plugs, 12" wire and a capacitor. Somebody figured that out and posted it here. The 10mf Tantalum capacitor everybody installs in the AFM stores a charge and filters the signal to the computer and prevents V.S. from occurring. I was lucky and found a factory Vanagon Syndrome eliminator harness in a junk yard and put it on. I couldn't get the van to stall no matter how hard I tried.

I recently had a VW Master Tech come to the house and rebuild my motor and he cleaned and adjusted the micro-switches on the intake and the AFM. He took that harness adapter off and put it in my glove box. He said "You won't need this. You won't experience V.S. anymore, I've fixed the problem, but I'll leave this here because I'm sure you don't believe me" 

 I've put 4,000 miles on it so far and haven't had a single instance. I'll keep the harness in the glove box for peace of mind...

Shawn
87 Syncro "Eeyore"
78 Champagne Edition Bus
80 Aircooled Westy L "Tigger" (for the kids)