I have got a standard engined, apart from a bailey dump valve (as far as I know anyway!), MY95 imported wrx. Over the past months my check engine light has come on for a while and then turned off and keeps doing this until the car is up to temp, and I was wondering if the dump valve could have anything to do with this as the check engine code came up with a pressure problem and I have heard that if a car is not running at 16psi or over it is possable to loose pressure through the dump valve. Any ideas someone.

 

When you say a pressure problem, it sounds very vague. The diagnostic code is a little more specific than that.
The only thing I can think of relating to pressure is the MAP sensor. A dump valve shouldnt have any effect on this reading that would cause a CEL, without causing serious running problems also.
Id check all pipework and connections on the MAP sensor, and possibly an ecu reset.
I had this fault code flash at me a few times after re-installing my engine. Did a reset and it has been fine since.
Its a wee small rectangular shaped thingy madey by Denso on the drivers side strut tower

 

Thats great thanks I will have a look tomorrow.