Originally Posted by
Strife
You should call a local state government office and ask them about emissions and get some necessary information. That way you'll be able to pick up a header that will suite your needs to be carb legal.
Considering money isn't a factor I'd say pick up that Mugen header. It looks absolutely gorgeous, however, Japan has different laws regarding emissions and the Mugen header may not be good enough.
I do believe that Japan requires every car to have a catalytic converter for street driving. So there's a nice selection of high flow cats there that can keep you carb legal in Japan. You may be able to source a high flow cat that was made in a way that could help you pass emissions in the states.