I hate this ambiguity that exists in this thread with regard to the offender. I am a strong believer in "personal responsibility", being responsible for your actions, the things you say and the decisions you make etc. To write off someones car and then simply reply with some weak statement like "oh it's a racetrack buddy" is a real cop out and a real shame.
So lets get to know our guy(s).
So the car is known as DriftZ, it is usually driven by Dan Mackie, and from what I can tell is owned by a bloke named Greg Stevenson (http://www.linkedin.com/pub/greg-stevenson/12/B99/497), who is also the owner/manager of the cars major sponsor Sureflo exhaust in Ingleburn NSW. Here is their website: http://www.surefloexhaust.com.au/frame1280x1024.htm
They are both respected members of the aus300zx.com forum.
Gregs username is Thunder and his profile is as follows.
http://www.aus300zx.com/forum/member.php?u=3585
I had a bit more info on Mr Mackie, but since it seems that he wasn't driving I won't post. However, the owners info is all still relevant, his car, ultimately his responsibility, so yeah shoot him and email and let him know what you think and if you are considering of getting a new exhaust might want to think twice about Greg and Sureflo.