Here ya go Gary, a boost activated exhaust bypass valve:
http://www.atpturbo.com/root/releases/release091004.htm
This is exactly what you need!
IMHO
Only problem is that the last time I talked to this company they said their valves are backordered and have been for months... That pretty much means they're unavailable. But someone else has to sell the same kind of thing.
To activate these I would just put a T connection in the line going to your turbo's wastegate valve. The air bubbler T connections used in fish tanks would work (as long as it's not in a high heat area), or you can buy T connections at any auto parts store. Then I'd run the hose from this T connection to the two bypass valves. If you want to control when they see the boost pressure, just put an MBC in-line with the hose. If you want a really cheap and simple MBC I can make you one. You could also put a solenoid valve in-line to turn the valves on and off. I used to source one from Car Quest. I'll have to see if I can dig up the part number.
Too bad I live in California. I'd love to work with you on this project directly.
