Your 97 E320, is it still the m104 inline six or the m112 v6?

I can tell you we just had a misfire problem on our vw eurovan, it was the fuel injector, and it ran poorly at idle but ran basically ok at speed. If your misfire jumps around, it is probably not injectors. How hard to change injectors on whatever 6-cyl you have? On the vw, about 18 hours the first time around, then 7 hours the second.

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2002 Mercedes-Benz E320 4Matic
1995 Mercedes-Benz E320 Wagon
2005 Land Rover LR3 V8 SE
1999 Audi A8 4.2L quattro