I ran mine at 10-12 psi for about 6 months before I got a BOV, you will hear some compressor surge...kinda depends on your turbo as well, I am using the mitsubishi td04 15t water and oil cooled turbo, and its made to be able to run w/out a BOV up to 12psi without any damage...some on the otherhand I wouldn't...I have the same BOV as you though I don't know about you but I hate the way the hks flange works, I expected better from them...but yeah I had my BOV shoot completely off the charge pipe (so pretty much had a 1.5 inch hole in my intake pipe) I was able to drive myself home w/ it like that to fix it and the car ran shitty but it ran lol. But yeah when the BOV shot off the o-ring fell onto the street and I couldn't find it, I just weant to an ace hardware and they have every shape and size of an o-ring you can think of, just go there and get one that fits nicely in the flange and one thats thick enough so when you press the bov on it it seals everything up...