I've just fitted the Willall cat-back Titanium exhaust system in conjunction with the Cobb Accessport flash using the Willall map for 98+ RON fuel. Initially, I considered the Akrapovic system but the value, the "home-grown" support and the performance offered by Willall swayed me in their direction. After a minor glitch with a scratched Cobb screen I got to drive the end result yesterday after having my Nissan dealer fit the exhaust. I've owned tuned EVO's and Porsches, ridden Superbikes for years and driven open-wheelers at track days. None have managed to combine the noise, handling and shocking acceleration of the GTR with ca. 630+ bhp. I bought the Cobb Accessport with TCM but haven't given it the 3,300 rpm launch so wait out for more feedback.