Its all just a delaying tactic to make it hard, so not everyone does it. My experience of customs are that if its one for your own use, they dont care. If its heaps of em to make a fortune, expect to pay handsomely.
The rules are constantly changing and can be interpreted differently in different circumstances. There is always a loophole or an exception in an Aussie system.
Eg : I have been trying to get my VR6 converted Ibiza to comply with an RTA emissions test, so that I can get it engineered. Having downtuned it, so that it just about runs, I was told by the RTA that there are no test slots until April. However, they did tell me that not all engineers require their test. I then simply rang round and found an old feller who has been an RTA approved engineer for years and was not interested in the emissions test, simply the modifications I had made and his fee!
Madness, but at least it will soon be legal and then I`ll get it tuned properly :twisted: