blitz sbc works in reverse!?!

[NORFY]

hey there guys, i recently bought a blitz sbc off ebay (i know) to fit my UK spec 200sx (240sx)

this is the unit,


ive had loads of trouble fitting it and found out that the loom and solenoid are not standard blitz items.

well its all fitted as the seller has said and it does seem correct, the unit appears to work perfectly fine on the road.

my problem is that when i adjust the boost level `up`, the actual boost pressure drops.
so my car is running 14 psi(1bar) and when i turn it up (hoping to reach 17psi (1.2bar) i actually only get about 8 psi(?bar)

i had another look today and think the problem might be with the solenoid, im sure that normal boost solenoids have three ports (in, out, and one to atmos) whereas this one ive been sent only has two (in, out)
and iirc you need the port to atmos to allow the boost pressure to rise.

does this sound about right? i mean does it sound like the 2 port solenoid is the problem?

many thanks, Mark