I had a problem just like that on my 190E. Basically I would set the mixture and then recheck it the next day and it would be diferent. Some days it was rich and other's lean. Replaced the Lambda tower and now it stays where set. Took about 15 minutes time to replace the tower. I would fix that first. Then screw with the EHA.

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~Jamie
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2003 Pewter C230K SC C1, C4, C5, C7, heated seats, CD Changer, and 6 Speed. ContiExtremes on the C7's.

1986 190E 2.3 Black, Auto, Mods to come soon.....