Yeah I grew up calling them extractors. Australia is becoming very Americanised.I'm interested too. Might check it out with the guys that have done performance mods to my cars and see what they say.
edit, checked with them and they said not worth doing unless you've done your headers (didnt even know what they were until I googled) and intake (have an Air Raid CAI), but once those are done it is worth it. so it looks like headers are next, at least one thing in my house can look forward to getting some head treatment.