Does anyone know if the 360 or 430 exhaust bypass valves operate via a solenoid or straight off engine vacuum? I have noticed that when a 360 or 430 is revved in neutral, the bypass valves open very soon and create a lot of noise, where as with the 355, the engine needs to be revved quite hard several times in neutral to induce the bypass valve to open. I have replaced my oem bypass valve with a capristo one which operates in reverse to the oem one (similar to the 360/430 which requires vacuum to close the valve). I was thinking of plumbing the vaccum straight from the engine to the capristo valve to get a more instant response from the bypass valve. Any comments would be appreciated.