If I was in SJ, we could meet.... stumbling can be an easy fix or tricky....
Tom's Mercedes Benz 108/109 Resource Site
Always start with the less expensive / involved part.... gas, fuel filter, the new gas with ethanol is a real headache, I had a few filters plugged up as the gas gelled, so I now uses the stabil for ethanol.
Vacuum leaks will create a nice erratic vibration.