I've heard of that before and I've completely taken off the flapper door on my stock turbo (rx7) divided the turbine wheel and the hole where the flapper door used to be at then mounted and external wastegate (tial 38mm) on the flange that goes before the downpipe. It works great with no problems.
New price $200
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Some people see what they want to see, but some others see what is. The world of appearance is more appealing than reality to many.