Hello fchatters I posted this in the technical section, but i had no replies, so i'm posting it here. I have a couple of questions regarding the f355 vacuum system for the exhaust bypass valve. Vacuum reservior tank - how does this work? i can see that there are two hoses connecting to it, one in and one out. The tube going out then connects to the two solenoid valves. When the engine produces most vacuum at idle, does this tank simply hold vaccum for usage when needed? When the bypass valve solenoid valve opens, vacuum is then applied to the bypass valve diaphram and the valve opens. When the solenoid valve closes, there must be still some residual vacuum because the diaphram rod takes a few moments to return to the resting position. 360/430 bypass - these operate in reverse to 355 one, needing vacuum to close the bypass valve. Do the 360 and 430 have a reservior tank? 355 capristo bypass valve - this is an after market bypass valve which works like the 360 one. Capristo supply an extra solenoid valve to do the reversing of vacuum. How does this work? Thanks for your help to those that respond.