iCarbon is still all made in Taiwan. There is almost no difference in iCarbon's quality vs the ebay stuff.
I've had both diffusers and you can look at my past thread where I made comparing them. Only carbon fiber piece that I have seen myself in person where you could definitely tell the difference with was the SleK 1M front lip I saw on Harold's car. That is the only reason I let SleK use my car for 2 weeks to make a front lip for the 135i and the same reason I will be picking up their trunk / hood when they come out. You can easily tell the difference between American made CF and overseas if you look at them in person.