Hi tinypanzer,

Thanks for your suggestion! I'm going to recheck the vacuum lines against the diagram, as I only checked for vacuum leaks previously. I don't see any soot or smoke coming out of the tailpipe and am going to fill up without ethanol to see if that makes any difference on the mileage.

Regarding the odometer, my car's a W126 and I'm going to try and get the gears swapped this week. I think I just have to unclip the speedo cable under the floor mats and yank the cluster out with the homemade tool. Hope I don't accidentally break anything while I'm in there!