yes there are limits
no i did not read this out of a mad or off a web site
a friend that has a b16 in integra a few years back told me this about the type r intake rember him? white and a lil primer lol
all im saying if your goin to buy an intake for a b18c why not get the 3"
im more than sure that a b18c can handel that any day
and you and me both know that a 4" exhaust is just stupid
by no means is that what i was saying or hinting
but you want less restrictions
if hes opening up the air on the b18c why not have the bigger intake?
the only restriction there for air going in is the TB unless he changes that out at the same time
same idea when you have an exhaust made
why use 2.25 piping with 1.75 *for example* flanges? or a small ass muffler? etc.........or a smashed up header
now who know if hes gonna run rich or lean with these bolt ons
there can be many different reasons why
but if hes going to the extent of a skunk2 mani and whit i think a VAFC would be a nice touch
hell anyone with a swap prob shold ook into one
im sure you can agree with me there

but in the end as i said before if your spending the price for the ls which is 2.5" why not get the ITR 3.0"