I am often an idiot so no controversity is intended about this post. This is a tip about improving your chances of getting a good engine part when buying used parts. I needed a secondary air pump. The new bosch part was expensive (list price $850 best internet price about $280) compared to an ebay listing for the MB part number for the same Bosch part. By looking for the Mercedes SL500 part (a little newer model car that uses the same part number) I was able to get a 2011 part from crashed car for $34 with shipping. Then I was able to buy the ebay square trade 12 month warranty for $8. I also like it when the junk yard seller lists the donor car details so you can get an idea of how much the part was used.