Any mods at all?

supercharged pressure relief valve 2 mate in the black box, i'll have money on it, as the primary turbo is controlled by this untill running its in twin turbo mode,anouther possible issue could be if u have installed an aftermarket bov

p.s i have a spare black box if u need one

No mods at all engine wise. No hoses replaced and factory re-circ BOV in place.Thanks for the input-i had suspected that solenoid a little as its the only one connected to primary turbo side in the solenoid box.

that primary solenoid doesnt do anything untill both turbos are humming mate , primary booost is controlled by that blow over valve thing next to the secandary turbo.

here is a r pill diagram i drew ages ago

the little black bov looking thing thats on the LHS of the throttle body controls boost until your over 4300rpm
the primary waste-gate then controls boost but restrictor pills will also cause you to hit boost cut if they aren't where there supposed to be ,


the next couple of images might help also



the bg5 is similar to the b4 , no map sensor and a few other little suttle changes