Are you sure that it was an OEM part? Cheap O2 sensors are all over the place. I don't trust anything that comes out of eBay. If you said you got it from Pelican Parts then it is worth comparing. Look up the same part on Mercedes of Atlanta web page to get the correct dealer pricing. And I don't begrudge the dealer his costs because of his overhead. Having said that, I go to an independent.

Anziani
'97 CL600 56K