I bought some fake GT500 injectors, and this is what I learned
 

In the last couple months, I noticed some GT500 injectors popping up on eBay for a fair bit less than I can get them for. In the ads for these, it's not clear that they are not Bosch, so I bought some to see what was up.

From the exterior, they seem really similar. The o-rings are slightly oversized and of terrible quality, and they are fitted with filters, which OEM ones are not. The molding is almost identical except for a couple of subtle differences that the average consumer wouldn't notice.

https://cimg4.ibsrv.net/gimg/www.mia...7d60d82fa5.jpg
The serial numbers are the same, and the date styles are the same The real one has a second set of serial numbers, and a QR code
https://cimg0.ibsrv.net/gimg/www.mia...a59437f0c9.jpg
Notice the sheen on the left (fake) is slightly shinier, whereas the right (real) is more matte
https://cimg9.ibsrv.net/gimg/www.mia...32df469132.jpg
Here is where we start seeing the big differences. The screen on the right is a 4-hole screen vs. the multi-hole screen
After this point, things get really weird...

https://cimg0.ibsrv.net/gimg/www.mia...a731620bf3.jpg
One of the great things about GT500 injectors is their dual cone spray pattern and excellent atomization. These have the "ID1000 gush". Look at that pencil thin stream.
https://cimg0.ibsrv.net/gimg/www.mia...99a5484b02.jpg
Now we get to the flow. You don't even have to measure to see that there is a problem here.

The average flow rate is 227cc/min at 3 bar... Wait, what? Yeah. I had to run them side by side with the real ones to make sure my machine wasn't broken. These are sold as 630cc/min.
On my new flow bench, the typical static flow rate range for a batch of 100 real GT500 injectors is about 5% (at idle it's higher, which is the main reason they need to be flow matched). With these, in a set of 8 the range was 14%. Could you imagine having one of your cylinders getting 14% less fuel under boost?

These particular injectors are so bad that your car basically won't run. But I think the main concern is that in a year or two these might get better enough that they at least output roughly the amount of fuel they should, but the quality and output is so downright terrible your chance of melting a piston becomes a near certainty. Buyer beware.

Lol at the molding quality difference.

A+ post. Threads like this are why I am terribly disappointed when I visit new forums for information. This community is amazing.

This kinda stuff is so sketchy. Thanks for investigating!

Thanks Nigel! You are a true credit to the forum, and to aftermarket parts vendors in general.