Having engineered a car here in WA I have a little bit of experience with this kind of thing - not a lot, but a little.
I know pod filters are illegel in WA, their reasoning behind it is, if your car backfires, it can set it alight. BUT and this is the funny part, you can go to the pits and they will write you a permit for a pod filter! I don't know how a permit will stop it catching on fire
I've just learnt to never question a Government department, they are ALWAYS right.
I don't know what type of car you drive, but any modifications to a motor after 1971 affect emissions (as you would probably already know), so are therefore illegal. The good thing with WA is, the Police don't have sniffers, so they can't check your emission outputs on the spot, at the pits might be different.
The bonnet vent question is right, but then begs the question, what about Toranas? they have a backwards facing bonnet vent? so do some Brock common-whores? and don't some model XR's (EL's)?
As for the tune up, I'm guessing you have a lumpy cam in it right?
Lastly, I know from mates in the force, you only have to go over the pits if you have a yellow sticker, if you are getting pulled over all the time, I would get the car engineered, we did this from the start and have a 4 page engineers certificate that stays in the car, just in case.
Hope this helps...