I'm also very happy with the TurboSmart BOVs - does the job without much fanfare and noise, and you need to look closely in my Q's engine compartment to see them.I know this thread is old, but I went the TurboSmart route. Much quieter than the HKS's. Just a whoosh instead of a whistle. I wasn't looking to draw more attention to my car. I'm 60 years old. If I was 25 or 30, I might have gone with the HKS's. They all pretty much do the same thing. It's up to the individual's preference.