Gordon,
There was a standard dump valve on your starlet doing exactly the same job as your new Bailey BOV.
But the Bailey BOV dumps the air (Left over when the Throttle Body butterfly closes) out into the atmosphere and makes the phsss noise as it does it where as the standard one dumps this air back into the intake system.
BOV's do not give you more power unless in the unlikley event that your standard BOV was leaking boost under pressure. It is more than likely just the wetter weather and some placebo which has caused the percieved increase in power.
This is your first post so I hope everyone doesnt rip into you. Every person starts off somewhere and if you are prepared to learn by reading information on this site then you will start to pick things up very quickly.
Dave