Few months back I purchased 8 of A0041598103. Sold as original equipment marked as MB.

The seller is from China with 99.4% satisfaction. Only 1 review was saying fake.

Beware, I had to replace all after 3,000 KM and terrible misfires. Problems started right after installing them.
They are fake!

 

Happened to me once. I will not buy parts off of eBay or Amazon. If you check the Reddit subforum titled " just rolled into the shop", you'll read many horror stories about counterfeit parts.

 

I would never even buy windshield washer from fleebay - They advertise "It fits guaranteed!" instead of "products are guaranteed" (refund limited to price of puchase... damages excluded.

 

find ways to save on labor, not parts.

 

Original equipment and Bosch/etc. on those sites are all replicas and they should only be purchased from reputable sources.

Usually you can notice immediately when your idle needle isn't sitting perfectly on RPM's. While they might not introduce a misfire immediately, they definitely are not operating as they should.