hmm...this is interesting...i have often wondered what the point of that vaccum opening is. No internal wastegates come with a separate vaccum opening as well as boost. My only thought on this is, wouldn't that vaccum pull the wastegate open even at idle? Because basically that wastgate has too chambers and a diaphragm in between. Boost pushes the wastegate open from one side, so i would assume vaccum would open the wastegate on the other side of the diaphragm. If anyone else has ever cracked open their wastegate, they will see what i mean. I don't know if that vaccum that is seen at idle/deccelleration is enough to open it or not. I am curious if anyone has tried this or not.

My other concern is that you would have a wastegate that theoretically wouldn't open under boost because you would have roughly the same amount of pressure pushing on both sides of the diaphragm that opens the gate. Unless you use some form of check valve to make sure it only sees vaccuum. I don't know, seems like way too much work since to get the gate to work properly, all you need to do is hook it up to the boost source fitting on the bottom and run that to the turbo boost outlet barb.

jason
95 GS turbo