I forgot the M110 was mechanical. I'm used to living in M117 K-Jet land.

The WUR is vacuum-based. If you have a vacuum leak somewhere (or your AAV is stuck open) the mixture will be richer than it needs to be. I assume you could test the AAV by taking it off the engine and trying to blow through it. If you can pass air through it, you know it's open.

Check that the idle stop screw isn't turned way in keeping the throttle propped open either.

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Current stable:
1995 E320 157K (Nancy)
1983 500SL 125K (SLoL)

Gone but not forgotten:
1986 300SDL (RIP)
1991 350SD
1991 560SEL
1990 560SEL
1986 500SEL Euro (Rusted to nothing at 47K!)

Gone and wanting to forget:
1985 524TD 167K (TotalDumpster™) [Definitely NOT a Benz]