There is no way of venting the stock piece. It looks like nothing more than a cap covering a hole with a nipple for the vaccume hose on it.
I have some pics ill put up later on. Its of the inlet of the turbo. You can actually see a cavity inside the inlet where the air vents back into the compressor blade. At a higher boost, taht cavity will become restrictive.
Im yet to take off the cap and take a look inside but I don tthink you can get away with just adding a flange in its place. Ill be taking a look soon to see if its possible though.