Thanks for the tip, yes I noticed that vacuum line but wasn't sure what it is for… I'll be careful with it.

I don't like to use aftermarket parts with these kind of gaskets so I found Genuine MB (104-010-21-30) at my local dealer… opening bid from them $106.56, negotiated down to $62.00… still you've got to be kidding me. Well, that's before I asked for 12 bolt seals… $13.50 a piece, negotiated down to $7.00… holy ****, $84.00 for 12 rubber O-rings I could get for $10.00. I'm not even sure how important these bolt seals are but, I don't like to take chances with un-known aftermarket parts when labour is involved.

On my SL500 (M113) I've already replaced 4 coils before 100,000, I should probably replace remaining 4 (original MB) but, finding bad one on this engine is pretty easy so I'm not concerned.

Swapping coils on M104, to find a bad one, is like playing chess… screw it… 3 new ones and be done with it.

Spark plug wires for this 97 C280… I can't find Bosch set anymore, MB NLA… I only see Karlyn-STI set. Are these any good?

The wires I have in there are Bosch Ultra-Premium 7mm copper core. They look new, clean contacts. Resistance rated @ 2K Ohms… tested with multimeter @ 1.9K Ohms