Please don't take this the wrong way....You didn't post anything about the procedure you used to check the blow-off. I've followed your posts closely, but I would point out that it might not be the "vacuum pressure" as you put it- it might be overboost. You also changed the exhaust. There are a lot of cases (google) where internal turbine wastegates become unable to reign in overboost when an exhaust and intake become much better. I only mention this since I don't want to see all your hard work grenaded! I may be entirely wrong, but I suggest you put a boost gauge on and check. It just seems very strange that your blow off valve would be constantly open without overboost or incorrect plumbing.