2003 GLS starting problems

My girlfriend has a 2003 GLS with about 20k miles on it. Three times within the first year, she's had the same problem... it will start, idle for a second or two, then die. It does this two or three times, then it just won't start. Right before all this happens, there's a burning smell while she's driving that, to me, smells like burning plastic. She's had it towed to Ourisman VW (Laurel, MD) each time and been told it's the impulse sensor, comfort control module, fuel pump, and starter. She was told each of these were replaced, although the invoices never mentioned replacing the starter or fuel pump. It's been about six weeks since it last happened, and the burning smell is back. :banghead: Any suggestions as to what this could be?

Also, when driving at lower speeds (below 40 or so), it runs VERY loudly and the acceleration is weak. It sounds pretty similar to my father's '79 Chevy pick-up with a V8. I have a 2001 GLS, so I know what it SHOULD sound like, and this is a lot louder. Again, any suggestions?