I also recently replaced my throttle valve with a similar looking Pierburg part as yours. So far, so good.

OE = Original Equipment. What was included on your vehicle when it left the factory. It has BMW stickers, cast or engraved markings with roundels or BMW on it.

OEM = Original Equipment Manufacturer. This is NOT OE. These parts are manufactured by a company (a manufacturer) that BMW hired to manufacture parts for them. For some parts or types of parts, there is ONE OEM. In some cases, there could be several OEMs as the production cycle evolved new parts could have been designed or specified and the manufacturer changed or new contracts granted. 99% of the time, the OE part that you remove from your vehicle will have a manufacturer's name on it somewhere. That's the OEM for THAT part. Just because Bosch is a respected OEM for a lot of parts doesn't mean they're the OEM for any or every given part.

Aftermarket = Not OE or OEM, quite simply. Jim Bob's Electric House says, "Hell, we can make that!", and does it and sends it to market. He has some electrical knowledge and a 3D printer and goes to town. Of course, not all aftermarket outfits are like that. Trico makes excellent windshield wipers for example. They are not OE and not an OEM to my knowledge so they are aftermarket.

Counterfeit = I don't need to say much here. Price to good to be true? Well, it is. These parts will look like a good OE or OEM part but there's always something off. Usually, but not always. Bosch oxygen sensors and some other parts were being counterfeit extremely well years ago and fooled a lot of people and confounded Bosch themselves for a bit.

"OE-like" = This one is new and I don't know how else to call it. These are the parts that look nearly identical, if not fully identical to OE parts but the OE markings are covered or otherwise obliterated. Ultimately, a properly produced and procured part such as this is OEM. I'll admit I'm suspect of these parts but if purchased from reputable sellers, the risk is likely low. I think the trust that a nearly identical OE part imbues can be used against some people so purchase carefully. As savvy counterfeiter might even price it competitively but not too low as to make it appear genuine.

More of my thoughts about "OE-like", I don't really trust the "ground-off-emblem-same-as-OE" argument. In fact, it's clearly not the same. It doesn't make me trust the part any more than a trusted OEM or true quality aftermarket part. In fact, if I were into manufacturing counterfeit parts, that's exactly what I would do: strategically place grinding marks with the OEM marking of my target manufacturer overall and then sell at a discount. People do that and burn the consumer quite successfully.

Most of my electric and electronic parts are OE while durable parts are mixed and there others that I very, very rarely insist on OE but might tack them on a larger order. My life is simpler that way. I like a deal like anyone else so I shop around and if you can establish a good relationship with the service advisor and the parts desk, you can save significant money on most parts. I know that's hard because some dealers are terrible, terrible businesses run by uncaring crooks.

Part of my decision my depends on WHO is selling the part as well. For example, I live very near a national online BMW parts specialist. I'm more likely to buy an OEM or even an "OE-like" or aftermarket part from them since they guarantee the parts they sell and I can walk the part right back in for exchange or refund. They even sell OE parts at decent prices. I would be much less likely to buy an OE-like or aftermarket part from an eBay seller 'cheapBMWpartsfast' (made up seller name, no offense given) or similar. Heck, I'd be suspicious of OEM parts from such a supplier.

Lastly, how hard is the part to replace? I abhor doing things twice. I really hate doing hard things twice. I despise doing hard and dirty things twice. A mass air flow (MAF) sensor on my M5? Takes minutes to swap them out so maybe I take a chance on a cheaper part. Cam shaft position (CPS) sensor? No way. OE all the way. That job is dirty and wicked hard. I might have to replace CPS every 100k miles if that. I'll pay once and cry once. Throttle valve on my 35d. OEM and even an "OE-like" part. It takes a little time to replace but it's fully accessible and only a little dirty.

Just some things to think about or don't.

__________________
8/2011 X5 xDrive35d Sport, Black Sapphire Metallic, Black Nevada Leather, Fine Burr Walnut Trim
2/2001 M5, Jet Black, Exclusive Complete Black Walk Nappa Point Heritage Leather, Black Cubic Trim