I had the same set up on a build that did the same thing yours is doing may be not quite as much but any how I would try this, remove the feed tube to the puke tank and cap the fitting at the manifold. Also block the drain back to
oil pan from the puke tank so basically bypass the puke tank all together. Now make sure your filler cap is a good vented one so the engine can breathe or if you have a set of valve covers with breathers in them use those as well for the test. Take the car for a good run to get it nice and hot and see if there is any change. If no change I would put a good cooling system stop leak in and try, this should help if there is a pin hole some where.
Good luck.