Currently, the law in Victoria states that:

"""New definition of probationary prohibited vehicle
(from 1 July 2007)

has an engine that has been modified to increase the vehicle's performance (other than a modification made by the manufacturer in the course of the manufacture of the vehicle, ""

So, technically, engine that has been modified as in the single engine unit itself being modified + turbo/surpercharging, which is illegal on P-platers for sure. They always check under bonnet for turbo/supercharging in P-plater's

What about changing the air intake using the K&N Typhoon intake (CAI) which is currently used for the Honda Si 2.0L (USA) = Honda Civic 2.0 Sport. Would that be 'legally' classified as an intake modification rather than engine.

the final thing looks pretty stock as the pod is tucked in the "Stock" airbox bottom and behind a shield and the original bottom part of the air box is retained. Would cops be able to tell the difference? (That the plastic tube has now become a metal one )

http://www.knfilters.com/images/m/69-1014TS_Eng1.jpg