You see all kinds of crazy shit that gets street driven in the US, UK and everywhere else it seems. In Australia, not so much. Most forum members are from the US, so to shed a little light on why Aus cars are poo, I'll share a few of the laws in place.
1. After market BOV's are illegal.
2. Cannot fit smaller than standard diameter rims.
3. Lowest point of the car that is not suspension MUST be above 100mm/4"
4. Carbon fibre/fibreglass, FRP panels, flares, doors, scoops are illegal.
5. Lowering blocks are not allowed.
6. Exhaust must not go further than the most rear part of the car (not including towbar's)
7. Cannot remove any emmisions gear (which basically means you can't upgrade carby's)
8. Wheels cannot stick out of the guards at all.
9. You need a modification certificate from a Government approved engineer for any mod you do (motor swap, turbo conversion, bucket seats, approved roll cage, change of seating capacity and so on)
10. HID's are illegal, nor any 'blue' light.
11. A gear 'H' patter must be clearly displayed near the gear stick.
12. All steering wheels, seats, roll cages, lights, hub adapters and so on need to be approved and tested by ADR (Australian Design Rules)
13. Suspension travel cannot change beyond 10%
14. Adjustable platform suspension (coilovers, camber plates, adj.arms) cannot be fitted unless a modification certificate is approved ($1000 usually, if you can find someone near by who is approved...)
15. If you are on your provisional license (when you finish your 1yr's on your learners licence you gain your provisional licence for a minimum of 3yrs depending on each state) you are not allowed to drive any car with more than 6 cylinders, forced induction, a power level over 220kw/290hp or which has a modification certificate.
Plus there are 100000's of other little tiny rules and law's preventing people from modifying their car's to their full potential. But it doesn't stop most of us, we just find ways around the laws, that, or learn how to dodge police.
Unlike the US where the police don't rape car enthusiasts as much, the police here will finger every crevace of your butthole at the drop of a hat. They have quotas they need to reach of cars to defect, fines to give, as to keep revenue raising up.
The perfect example is one little famous Corolla that lives in Aus and HAD street rego. Everything was certified and legal, until the police raided a Huffy slider meet and blocked the roads so no one could leave and defect 50% of cars, even though no cars were doing skids/revving their motors. Thus defecting one of the best true JDM rides in Aus.
In Australia, it's impossible to modify your car in any way without getting hassled by the po po. Anyway, that's my rant out of the way.