While I have bought a set of replica Supersprint headers and a replica Supersprint rear exhaust for my E36M3, I have also bought a real USA Supersprint midpipe, a real Euro Supersprint midpipe and a real Euro Supersprint rear exhaust for my E36M3.
You could make a career out of criticizing those who buy replica products. Who first made the CSL style wheel, for example, that Apex, VMR and others replicate? Many forum members have bought those replica wheels.
There is no patent on the x-pipe for these cars. Anyone who makes one is subject to having their design copied, unless they actually create and patent a certain process or idea. So far, none have.