Recently there has been a surge of name brand counterfeit items being sold on eBay that are coming out of China.
You can easily spot them by the lack of the brand name being cast into the body.
Such as the GReddy blow-off valves, and HKS waste gates.
All the smaller GReddy BOVs have the word "GReddy" cast into the side of the body, just above the left mounting bolt (when looking at the discharge). The counterfeit ones just have a blank pad there.
HKS waste gates have "HKS" cast either on the top of the dome, or in the case of the really big ones that come with the anodized dome, have it cast on the side of the main body.
And many of the turbo manifolds are Chinese also.
Hint: If the seller has a bunch of the fake blow-off valves, and waste gates, most likely the rest of his stuff is out of China also !