Hissing noise
 

When I'm accelerating slowly with my window open my zs makes a hissing noise when you get to about 2 and a half thousand revs, sounds kinda like a dump valve, dunno if it's coming from the exhaust or somewhere else, sounds like a real ease of pressure, anyone know what it is?

Sorry Adam, I can't remember if your zs has an induction kit on it or not? Mine where I have a custom inner wing set up with the breather pipe being a length of silicone pipe going to the alloy tubing further down does make a big hiss / sigh when you turn off and often chirps on acceleration or gear change. Strange noise but I quite like it to be honest and has never caused problems so far.
I do also sometimes get a funny noise from my decat but I think that just needs looking at.
Possibly worth checking all connections on induction side especially if it has got a kit on it just to make sure no air leaks or anything like that maybe.