"Current legislation requires that all vehicles are fitted with a catalyzer
to reduce emissions and protect the environment.
Since the R35 stock catalyzer is authorized as a low emission one
even if it has the sport engine that the exhaust amount is 3.8L,
it naturally increases the exhaust resistance.
On the contrary, Mine’s Super Catalyzer II for R35 GT-R is totally compatible
with the sport engine’s performance and also completes the purification action
Suitable Model: R35 GT-R VR38DETT
Exhaust gas certificate included
Main Pipe diameter: φ70 x 2 → φ80
Unit Price: 218,000 yen"
I have to look and see what they claim for a horsepower increase. Something like this is not legal to replace in the US on an emissions controlled vehicle.