There's only one (1) . . .
O2 sensor in your car; it's located just ahead of the 'Y' in the exhaust system.
Yes, it's true! the newer sensors have a (very!) long pigtail and that's what Bosch now makes which works for 15 (I think) Mercedes models.
What you need to do: use two (2) cable ties and coil it up so it's apx the same length of the original. That shortens it so it won't rub on the drive shaft.
I replaced mine recently (104K miles) and the car has more more 'pep'. My gas mileage dropped a bit and it appears that the new O2 sensor restored it, around 15mpg city, 21 highway.
Regards . . . . JimF
'94 S500 Cpe
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