My mate has got a my94 wrx and he has a couple of module's in it that i am unsure what they are or what they do.
one is a HKS Electronic valve controller, with an lcd screen with figures that go from plus to minus as you rev the engine.
The other is an Airflow restrictor which is black box with two little *****.

any help as to what these are and what their uses are would be much appreciated

 

photos would help ???

 

This is more or less exactly what it says - it's boost controller, which allows you to
change boost values.
But best idea is to not touch it unless you know what to do with it.
Don't simply think you can easily increase the boost value and enjoy the power - it's the best way to blow the engine.
Those changing values on the screen are, I guess, monitored pressure/vacuum values while you/your mate drive.

Cheers
Jacek