the P0455 code I was getting on my '97 E320 was cured by putting a shot of WD40 into both ends of the purge valve which lets vapors from the fuel vapor recovery system back into the intake manifold. On my car this valve is located up next to the left front fender liner. (However info I've looked at indicates this valve may not be used on the E420.) Bad fuel tank cap could be the problem as well. Try flipping the gasket in the cap over. (Does the low fuel light flash when there is plenty of fuel in the tank?) The other codes could be caused by bad igniton coils, bad plug wires/conectors and who knows what else. A trouble shooting exercise recommended by some of the veterans is to move some of the wiring or coil associated with the failing cylinder to see if the problem follows. Best to move one thing at a time. There is one coil for each cylinder. I've tried to attach a photo of one.

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