Guys, Ive decided on the exhaust im going to get (Billy Boat triflow), but im unsure of the following Should i go for 2.5 inch diameter pipes or the 3 inch diameter? (talking about the actual pipe sections as opposed to the tail pipes) Obviously im going to have to go for the 3 inch de cats with suitable downpipes, but is there such a thing as having too little back pressure in the system? This is the rough engine spec i intend to be running to match the exhaust: Z1 side mounts Nismo 555's (for a '95 car which i think are running 610cc's) JD ecu K&N intake and probably Profec boost controller at around 15-16 psi mark aquamist water injection And prob an uprated fuel pressure regulator Now im taking a stab in the dark at these should make the engine run over 380fwhp and 350 lbs/ft (guessing from how steve 300zx on the UK forum '96 TT running is running 406fwhp on stock internals and tubs) Now with the rough guess in figures, would i be getting anywhere near the maximum flow capacity of a 2.5 inch system, or would a 3 inch system be worth investing in? Ideally in the future, with new tubs & internals, id like to run around the 450 rwhp/450lbsft, would a 2.5 inch system be able to handle this or should i save myself some money in the long run and go for the 3 inch. Over to you... Nick
