Got mine when my friend wanted to get Injen CAI for his S2000 so thought we would be smart and save on shipping together... But then we got slammed on custom fees... *dob*
Check out ebay.com & type search Injen Acura TSX, buy it from there.. Don't think anybody in Australia is a distributor of injen....
G'day Baboo, I passed you this arvo infront of the brewery on Milton Rd
I'll have my Injen within a week or two as it was sent to me last week. I got it for $195US from www.optionimports.com with free shipping to the US (It's gone up in price now). Fortunately I have a few friends and work colleagues in the US who act as intermediaries for me so I purchase it online, have it shipped to them and then they remove all the invoices repackage it with kitsch gifts and other mod parts, and send it off in two lots a week apart.
There are quite a few US online stores that will ship to AUS, the hard part will be avoiding customs duties.
They won't necessarily charge you. It's up to them to determine whether it's a genuine gift and waive the charges. It's more common for this to happen on regular post items. If you get something sent via evil FedEX, UPS, or DHL they'll definately hit you up with tarriffs.
Customs Duty on car parts is actually 15% of the value of the parts including shipping. You will then be charged 10% GST on the whole lot as well, so add approximately 25% to the cost of the parts.
By the way, Customs Officers are not stupid and they will know exactly what you are importing and what it is used for and approximately what it is worth. If you get through without paying any money on parts worth more than a couple of hundred dollars, you should consider yourself VERY lucky.
I’ve had my friend label the customs declaration label with exactly what’s inside the box. And indicated the value to be 2/3rds, up to exactly what I was invoiced minus shipping on the label. However the contents of the package is varied greatly, not to the point of looking deliberate, just enough so that the auto parts are equalled out by non-auto related, and non-masculine items. There’s no invoices within it at all, and genuinely will appear to be a gift (which it is – just that I’ve paid for it).
I’ve not once had a problem with Customs when returning to Australia, with gifts, and items well in excess of the tax-free limit. I just make sure I declare everything and am forward with the information. As a result those good guy’s just welcome me through! . I know it’s different when a person is accompanying the items, so fingers crossed this works as well.
If it doesn’t it’ll be less than $100 that I’ll have to pay so it really doesn’t matter as I’ll still have saved a few hundred in the long run and done the right thing. J
Bringing parts in with you through the airport is much easier to avoid paying customs duty/GST than it is when you just have them freighted/mailed/shipped to you.
I've brought back chassis bracing, three point strut braces, Cusco LSDs and thousands of dollars worth gauges and electronic controllers without ever paying a cent in customs duty/GST when holidaying in Japan, but only just managed to talk my way out of paying it on the Injen CAI and Hondata heatshield intake manifold gaskets I had shipped over.
All I'm saying is never assume that you won't get caught or that writing "gift" or "returned for warranty repair" will necessarily get you through.
. I know it’s different when a person is accompanying the items, so fingers crossed this works as well. 
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