Hi i have a 56 plate focus st its running around 300 bhp and alls been fine but started a fault runs fine from cold and up to temp but once warm and switched off the next time you drive loss in boost sometimes only quarter of normal and can hear loss of pressure (hissing )not sure back into system or to atmosphere could this be the solenoid ??

 

do you have an aftermarket dump valve on the car ,I had the same issue which turned out to be the piston sticking in the bailey dump valve when it got warm

 

Hi yeah got a bailey dump valve to but was doin it before that thought it was my diverter valve thats why i put the dump valve in and blanked the diverter

 

Hi yeah got a bailey dump valve to but was doin it before that thought it was my diverter valve thats why i put the dump valve in and blanked the diverter