Same thing on my X-wifes 2001 Jetta IV....it went limp mode a few times and was always a grip of cash to fix. Now that I think about it, the stupid thing went into limp mode on our wedding day. I should have listened to karma that day!! Would have saved me a sh!tload of $$!!! LOL
Mine has done this a couple of times. The first few was with the Unichip (see old threads). I disconnected the battery, removed the Unichip (after stranding me in the middle of nowhere, returned the battery leads and voila, it worked.
Just last week though (more than a year after the last time it stalled and limped) it fell dead and would not go over 12 or so miles an hour. Got it towed to dealership and they diagnosed it as a bad MAF. $300 later and it runs like a scalded ape- the way it used to before the Unichip.