im after a new exhaust as i've put mine on the wifes car to quieten it down. when would a 3" full system be needed over a 2.5" full system.

 

Over 400 bhp really.

I am gutted I put a 3inch on mine, as lost the low torque. not loads but enough to notice.

 

hmm decision time then my spec is as follows hopefully someone will say if i'd benefit from one.
sti version 8 bottom end,
polished ported sti version 3/4 heads and cams,
550 injectors,
parallel fuel rails and fpr,
front mount,
tubular manifold ported to match heads,
3" bell mouthed down pipe,
td05 20g turbo,
will be running simtek mafless when finished.

think thats it

 

if i had that spec i would get one on. : )

i have td05 16g and putting on a 3inch with 3inch bellmouth decat made a nice difference.

felt as though the turbo spun up quicker. and people say when i drive past you can really hear the turbo whistle, at low and medium-ish speed

 

You could go for the 3" when all your mods are on the mapper will make sure its set up correctly so no torque is lost, what sort of figures are you expecting once mapped?

 

not really aiming for figures more interested in how it is on the road, around 350 would be nice.