The rules are only specific on intercoolers and filters, anything else doesn't seem to matter so long as sensors etc are retained.
1. Intake systems
Intake systems are designed to ensure that the correct
air/fuel ratio is available to the engine for the cleanest
burn to minimise exhaust emissions. Systems that
provide excess air or fuel can create high exhaust
emissions from the vehicle. Fuel or other hydrocarbon
vapour that escapes as evaporative emissions can lead
to the formation of photochemical smog.
Replacement air cleaners are permitted provided that
they have all connections and systems present on the
original air cleaner and operate in an identical manner.
(a) Open element or pod type air cleaners on
carburetted vehicles are not permitted.
(b) Dry element pod type air cleaners are
permitted on EFI vehicles. Oiled, oil-soaked or
fluid-treated elements are not permitted. Any
sensors integral to the original system must be
retrofitted to the same approximate location.
© Intercoolers that are larger than standard or
have a different mounting location or are added
where none were originally fitted, are permitted
only if no other changes to the intake system
have been made. In other words, you may have
a pod filter or modified/added intercooler, but
not both. Any sensors integral to the original
intercooler or intake system must be retrofitted
and be in the correct location.
Note: aftermarket turbocharging kits that
include intercoolers that have been type tested
(ADR certified) for the model vehicle are
permitted. Documentary proof must be
retained to substantiate this.
(d) Airflow meters must not be disconnected. They
may be relocated, provided they are
functionally equivalent and are in the same
approximate location.
(e) Modified or aftermarket plenum chambers or
throttle bodies are not permitted.