hi steve it did used to work very well i tested the system and there was no pressure drop until you let off the gas.. it was an expensive bov cost me £165 but if its playing up maybe its best to get a new 1 mate (Y) p.s hope the cars still going well mate
alright lads the ufo controls and holds the boost pressure between s/c and turbo basically. you can fix it by putting in the oven for 10 mins on 100 degree's basically it fills with oil and blocks the diapham inside and then you get fluctating boost.
just make sure its upside down in the oven...
im here steve had every single pipe off and back on again for new silicone mate if ya need me shout i also have a laminated schematic that the lads posted up of all the vacuum system if ya get stuck which i will give ya sunday