If it matters, I have a legal exhaust with a metalcat... while it's no track monster it's certainly not gutless (250rwkw).
If Skyline owners are going to so careless about adhering to the law in this regard, don't we just have ourselves to blame when wondering why we're targeted as hoons? I for one hate the old POS silvia who cruises past my house daily with a 100+db milo tin, does nothing but give the rest of us a bad name.
To my knowledge QT used to carry out spot checks on emissions - mainly targeted at vehicles running Super - aside from that I'm not sure, have never been defected.
Also, before bitching that I deviated from the OP, note that I merely followed the direction the thread was taking.