in Sydney you can go for the "im240" test at the EPA for no cost.
you need to do this to have an intercooler engineered.
when it comes to top mount turbos, after market intakes, intercoolers, wastegates, BOV's as long as everything is plumbed correctly and the car is passing emissions there is no reason why it can not be engineered.
obvisouly anything adjustable E.G Fuel reg, computers & controllers "should not be passed as it can be "adjusted"
a roll cage can be engineered it need to have certin clearance of drivers/ passangers head in accident etc.
most things can be engineered it just comes done to how its done