After letting it heat soak in the garage, just took it out again for about 10 minutes and 3 miles. Really concentrated on the light to moderate throttle from a standing stop (since this was where the flat spot used to be) and the problem is absolutely gone. Again, am I out of the woods?

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08 W251 R350
97 W210 E320
91 W124 300E
86 W126 560SEL
85 W126 380SE Silver
85 W126 380SE Cranberry
79 W123 250
78 W123 280E
75 W114 280