I've had the stock Kerker 4/1 on a VMax, and Kerker 4/1's on a couple Kawasaki inline 4's, KZ750 & KZ1000. Also had a V & H KZ1000 4/1 bike.
I have a Kerker 4/1 in stainless steel for my FZR1000 that I've never installed, sitting, just waiting & a pair of aftermarket carbs for it. But, I really don't have the time to mess with it now, so it sits.
The Kerker 4/1 sounds just great at idle, it always manages to make people turn their heads to see what that bad sound is? It sounds like I'm back in about 1967 at the dragstrip and listening to some alcohol-burning small block Chevy in a Chevy II 2 door body, with a full roll cage, straight front axle and wrinklewalls getting ready to stage.
Those were some times, if you didn't go to college, within 3 months of finishing 12th grade, the POTUS sent you a letter, "Greetings from the President of the United States..." and that usually included a free trip to SE Asia, after boot camp.