Bought this wagon @ 6 mths. ago with bad head gasket.Replaced gasket,now tach is inop.,though if I tap relays next to battery tach may work and engine surges.Though I've been a tech for many years,I'm not real knowledgable with M.B..Would appreciate any input. BTW,I've already taken some of your suggestions with good results,such as ALDA adjustment,removal of AFM,etc..Excellent site.