The DV26 or 'EVO' twin piston dump valve is designed for turbocharged cars that have fuel injection with an airflow meter or metering unit.  The ingenious second piston allows cars to idle perfectly and for the fuel mixture to be unchanged which resolves all the running problems traditonally associated with diaphragm valves.  It has a 25mm push on base and comes supplied as standard with a straight 4mm polymer push on vacuum/boost connection.  The DV26 has a 60psi boost capability.