You should do a boost leak test before buying another one. Plus you will know for sure your BOV is bad if you can hear it leaking.

Here is how to do a boost leak test: http://www.vfaq.com/mods/ICtester.html. I would do one every time you change a part that could leak boost, like the BOV. Bookmark this page as it is very handy: http://www.vfaq.com/index-main.html