As above would like to know if there is a big benefit of fitting a 3 port boost solenoid before my map on my03 wrx if so has anyone got one lying around.thanks

 

Got one from my classic, £30 posted to GB

 

A boost Sol is digital, so pulses to let pressure out and therefore keep the gate closed and this gives you higher boost. The amount of pulses the sol has to do is called the duty cycle. If you use a 3 port the duty cycle is less, and mappers prefer them as the boost control is better due to the lower duty cycle, gives them more scope.