I had the adapter and the stupid EBay HKS SQV BOV. It ended up selling it for $30. The BOV was a pain to put together even with C-Clamp pliers and the BOV was too big to get any tools in to tighten it down without taking apart a bunch of stuff. Also make sure you have the BOV facing the EXACT angle you need it to face for install, because once the C ring is in place, you're done. I had to take a hammer and try and move it but ended up giving up. I ended up going with the Boomba BOV. All one piece, bolts right on and no adapter. But yes, you can still purchase the plate and make it work. Just be prepared.
Same here I had the eBay HKS and switched to Boomba, save your money and get Boomba or go adapter route and get a real HKS. They have a group buy for the Boomba bov
The C-Clip is no joke. I've got an SSQV on my WRX and it was a hell of a time to get it secured to the flange. I took the whistle fin out of my SSQV. BOV functions fantastic, but it's not very loud.
You gotta be really careful buying the real deal now. The fakes are so good these days, it's VERY hard to tell them apart. Buy from a well known reputable site only. Don't pay $200 from GoFastRicerParts.com because you found them to be a good deal on Google. You'll end up with a fake and never know it.