Unbeknownst to me when I purchased it, the HKS SSQV blow-off valve apparently has different sounds/tones available depending on the nose piece installed. And, in my first for-looks/sounds-only, non-performance mod in years, I swapped to HKS' lower tone SSQV insert.

Originally it came with the silver 3-spoke insert, and I replaced it with the purple round insert.