You might check out www.mercedesengines.net. I think they redo heads both on an exchange basis and on a recondition your head basis. I think for a M116/117, it is around 390 per head, excluding R&R costs obviously. From what I hear this place is a really good company that knows what they are doing. Keep us informed on what you decide to do and how it turns out. My idle isn't exactly smooth either!

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'86 420SE Euro
904 Midnight Blue, Gray Velour
Dad bought it new, now I own it.

"A Mercedes-Benz is like a fine wine, it only gets better with age."