In terms of BOV the general consensus on here seems to be that the standard factory fit valve is the best one for a standard engine. If you change it you will see no improvement in performance and probably even lose a little bit as the engine is taking air into account that is no longer there i.e. it's being vented to atmosphere instead of back into the engine.
The only reason to fit one on a standard engine is for the sound it makes and the same two names come up each time this is asked and they are HKS or Blitz.
Some people also experience idle problems and stalling with a VTA valve but there is no hard and fast rule. Fit a Blitz on one car and it runs ok, fit it to another seemingly identical car and it stalls when you lift off at high revs. You just have to suck it and see I'm afraid.
From memory the two valves I mentioned will set you back around £200.
PS: You will need to change the standard valve if you up the boost as it tends to leak if you go much over 1 bar but you can also buy aftermarket valves that vent internally just like the standard valve does if you dont want the noise or the idle problems.
slighlty gutted cuz was lookin forward to sum noise but by what you say its abit iffy!! mite go for blitz cuz every1s got the HKS BOV!
So why do the rallycars have the chatter on lift off? isn't that sum sought of BOV??
As said above/before............factory unit is ok upto circa 1.5 - 1.6 bar, where it has been found to leak..............APS do a dual vent one, which acts as a re-circ valve, venting back into the system(quiet) and as boost is increased vents to atmosphere.......so best of both worlds................tho' not sure how load it is or what boost it requires.....I think it's adjustable.not sure.....but do know it's about £160
The bailey DV26 which i have on mine is working a treat.
Its a twin piston valve which as far as im aware, lets some air back in to get around the air flow meter which solves the idling problems and stalling.
Im not sure if others have had any problems with the valve im using but i've had no stlling or idling problems at all.
Also just to add, I fitted a blitz jobbie to mine and was lucky in that I havent had any idle problems at all. I found a second hand one off here to keep the cost down rather than buy a new one just incase I did get stalling and had to take it off.
In terms of sound, its loud as hell and scares grannies up to a distance of at least 100 feet