I'm very interested in this and getting tired of my muffler delete.. I've always wanted to use the wastegate from the stock exhaust for something.
Well the stock exhaust has some kind of vacuum flapper in it. This probably won't be using a vacuum flapper as they are prone to leaking and sometimes don't sound good. This will be using a wastegate which is more expensive but I think it would turn out better.
The car comes with a constant vacuum source from the engine all the way back to the tail where there is a solenoid which flips this vacuum source on and off, which controls the flapper. This solenoid is controlled by a pin on the DME I am assuming, and connects to the solenoid through some kind of connector. I intend to find out what the part number is for the connector so I can wire up a very small wireless receiver box I bought. This box has a fob, which runs on the same frequency as the homelink, so hopefully that works to toggle it on and off. The vacuum source itself, would need a Y splitter to go to both wastegates.