ive got a s2 erst and want to run 2 stage boost. i understand its just a matter of cutting into the earth connection on the amal valve and fitting a switch. im currentling 1 bar of boost all the time and would like to run about 0.5 -0.6 bar on low boost setting, just to see if it would work i disconnected the plug from the amal valve which you would imagine would be the same thing as switching it off, but the boost pressure still remains at 1 bar. can anyone help me??