Heres the story, I drove my 1991 Westie Syncro on a almost cross country trip over a couple of months. On the trip out we drove non stop (except to fill up check the oil and take restroom breaks), didn't notice a thing wrong with the vanagon it ran great. we spend a few months in west Texas, during this time we took the van to town for the day every week at least during this time I notice that it was sometimes run rough for a second or two and then good as gold no rhyme or reason to when and where. When we started back to the east I pulled off to get gas and do the on the road routine. After a fill up and break I will say it was ten to twenty mins. I started off again the van started fine a nd ran great but when I would give it gas and let the clutch out it would act as if it was dying not jerking just like some one was pulling all the power out as soon as the clutch was engaging. If you pushed in the clutch it would not die it would return to idle. Sometimes it would repeat this on the next cycle of the clutch sometimes not. If it did die it would always start again easily. And then it would fix its self and it would be fine until you stopped again and shut it down for a while. This bus has the stumble fix from VW . I'm just a little confused, I took it to the local "expert" and he replaced a temp sensor that fixed my cooling fan issue but the loss of power it got me. I'm about ready to replace the air meter as that is the only other thing that comes to mind. I ve checked all the obvious things wires, fuel pressure  Please help my vanagon run strong all the time Thanks Scott