I've just found some for sale on 'tinternet and wondered what there purpose is?

 

To allow the gas from a wastegate to get out as easily as possible.

Forget ever doing trackdays again though, other than the occasional full noise one, as you'll get chucked off pretty much everywhere.

Ive routed mine back into the exhaust instead, so its still silenced.

 

do they offer any performance gains? how do you fit them? (would be on a rst with a T3)

 

You dont need one on an internally gated t3, there would be no point, it would just make a lot of annoying noise and gain you nothing.

 

Thanks for the advice mate, will leave them alone then