I'll add an endorsement for Timevalve. Put one on the 400e for the center and rear mufs. Comes with a as long as you own the car warranty. Less expensive than OEM and as Steve pointed out, will probably never wear out. If I remember, they use high nickel and chromium content plated stainless steel. The guys that installed it said it was as difficult to work with as any MB they worked on before. Which, I guess is a complement. Anyway it is quiet and no problems in the first 2 years of use.

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...Tracy

'00 ML320 "Casper"
'92 400E "Stella"