Per usual, IJ has hit the nail on the head.
There ARE a lot of people that run the knockoff FiAL & HK$ wastegates (as well as blow-off valves) that have great success.
However to my knowledge, most of them at least tore it down to inspect for clearance issues and if need be, replace some of the internals with authentic pieces (Most of these things are interchangable as the knock-off's are almost 100% identical as far as the actual design goes.
I've been there...I've done that.
A knock-off TiAL that I previously owned quickly became Authentic (Other than the main unit itself).
Of course, nobody can guaranttee success...and that's just a risk you're going to have to take.
"Best bang for the buck" is okay...but if you're even considering being cheap with a Supra.......Don't plan on your journey lasting very long.
Jeff