My bus has been running fine for years (I admit with minimal maintenance, except to pass emissions). The other day I pulled up to a light and when it turned green, I pressed the gas pedal and I barely moved. After crawling for about 20-30 yards it picked up and ran normally but it felt strange the first 2 or 3 times I had to slow down. I made it to my destination and then came back home without further incident.
Any ideas what might cause this? I did have my gas pedal cable replaced a while back but I don't think it was that. My van did recently fail emissions which I have not had time to get looked at yet - so it is probably out of tune. But I'm wondering if this could be a warning of something more serious.

On another note, how easy is it to replace the fuel injectors? Can I do it myself? And how easy is it to replace a catalytic converter and oxygen sensor, can I do that myself? The last time I took my van in for emissions work, it cost me over $1000 so I hope to avoid that again.

-David (1987 Wolfsburg)