The old models that I think are like the ones on eBay have a 3/8 inch bypass in the housing to let excess pressure through to the exaust. The new models I have don't have the bypass holes and will create more boost so I added wastegates to control the presure.
The bypass holes were added by the different people selling them, either Banks, PFM or Race Aero, perhaps a couple of others. When I worked for Gale Banks we had fixtures with drill guides, 1/4", 3/8", 1/2" and 5/8", depending on what level of boost was needed for a specific kit or engine.