HKS 1st Gen Sequential BOV 

 What I have read about it so far "🔥🔥🔥The sound is very settle 2 tone low smoothing sound unlike 2nd Gen SQV higher pitch🔥🔥 ".   True. Depending on the RPMs and how quick you release your foot off of the gas pedal, along with the primary and/or secondary valves opening makes several different sounds. Not sure it like the supercharger and wishes it was on a turbo! This one struggled. This one could of been made as early as 1994 which is a piece of JDM History(https://mashimarho.com/products/n54-blow-off-valve). The Old school bov has adjustment screw on back, as the newer ones dont.

I had to use the big vacuum port right behind the throttle body. This is because it would stall on opening on the small vacuum ports. Not sure if it is because it is a pull type vs. push, but the for the Greddy's I did not have this problem.

The secondary valve does not sound so good when it opens. I tried cleaning it really good with safe cleaner to see if that would help. It somewhat but still not the best sound.