Originally Posted by the evil i

what exactly do you mean 5ats dont have 280hp. are the engines different or osmething?

Originally Posted by fatlip

I meant if i get the spacer ztube and hfc would i need an aftermarket exhaust?

Originally Posted by gary c

Five years ago when our G35s were really popular in the import mags and they were doing bolt ons and showing the results on a dyno. Stillen advertised it's dual cat-back exhaust to give you 18 RWHP the mag showed it fell a couple short, still not bad. MotorDynes 5/16" spacer has always been a very popular mod and will add at least 10 HP by correcting Nissans design flaw. OE cats is where the biggest restriction is and the answer is either HFC's or test pipes. I wouldn't recommend test pipes as they're illegal and a few will make a major rasp sound. HFC's should give you another 10 HP! Intakes if you believe the manufactures will kick in another 10+ HP but we all know that is b.s., you might get 1 to 3 HP if your lucky but the sound along with a z-tube is invaluable....
Gary

Originally Posted by Revo

The intake gains will be negligible. Exhaust might be a loss depending on which exhaust you get. So anywhere from -5whp up to +10whp.

The HFC will be the most beneficial and net you 10-15whp.

However, remember that mods don't stack linearly. A good estimation I use is to square all the gains, add them together, and take the square root of the sum.

For example, 3hp from intake, 5hp from exhaust, 10hp from HFC.

3^2 + 5^2 + 10^2 = 134

Square Root of 134 = ~11.5