I mean, there are a couple of options available for this car, such as a Borla or RR Racing, and I'm sure there are more.
However, the Joe Z system was created in the states by a mechanic/tuner who owns an IS F and spent good time and effort in order to perfect the design and development, and many IS F owners over there were able to source the system at a reasonable price given it was manufactured locally.A lot of them began to respect and appreciate the quality of the system as well as the proven power gains, and the forums started to become inundated with suggestions of installing the said system.
Given the word was being spread, us overseas owners would rather purchase and install a product which is being raved and respected due to the substantial time and money spent on sourcing the product. Not to mention that at one stage, Lexus of Sydney and Brisbane were importing them particularly over its rival counterparts to offer to IS F owners as an aftermarket option.