I'll be honest. They were the best thing i ever put on the 350z, they complimented the milltek perfectly andi would recommend them to anyone.
On the 370z initially i thought wow, oh god that sounds awesome, put your foot down and its like a full blown racer. But thrn you have to live with it every day. A couple of days later I got into the car at work and started her up and felt embarrased, it was too much. For me it took the stillen one stage too far and it didnt work out as well as on the 350z.
Every so often, especially in wales with my buddies and their louder cars i feel the stillen may be too quiet amd think back and say should i try it again, however out on the country roads, roof down and the stillen singing away by itself its glorious. Would i go for hfcs now, definitely not.
Also forgot to mention, with the hfcs on the 350 they kept firing off the ecu light with air flow issues, was a real pain, especially when cold. Really didnt want that hassle again with Rosie.