Skidude, that whistling sound you are hearing is common to the BOV's from that site. Joemazda on the mazda-speed.com forums has a fix for it. I can't remember what it is but I know it is easy. If you pm him I am sure he will let you know. I have one of those BOV's on my car and I got it with a kit he makes. He fixes the problem with the kit so there is no whistle when I drive. Just thought I would give you a heads up.

 

Thanks, I will look into that and be much happier!