Examples of minor (owner certified) modifications are:
„ Engine changes where the capacity increase is less than 15% above the maximum size engine available for the
vehicle (providing no major structural modifications are necessary and where noise and/or exhaust emission
ADRs apply, all standard equipment such as carburettors, exhaust systems, exhaust gas recirculating valves,
oxygen sensors and catalytic convertors relating to noise and emission control are retained and operate
correctly).

http://www.rta.nsw.gov.au/registrati...s_nov_2007.pdf