I had a problem where my car would fluctuate around 50% at idle but upon any application of throttle, the value would slowly drop to 0%. I thought that my car would we puffing out white smoke when it reached this value as I believe this means the mixture was getting way lean... anyways, a good used replacement EHA solved the problem.

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2006 BMW M5 "Heidi" @ 109,000 miles
2005 MBZ C55 AMG "Lorelai" @ 165,000 miles
1991 MBZ 300E "Benzachino II" @ 165,000 miles
1990 MBZ 500SL "Shoshanna" @ 118,000 miles

(On the hunt for a good used M103 engine as of 6/10/23, PM me if you have one to sell!)