[silver]

you can get huge gains from intake and exhaust modifications, but most people think of an aftermarket intake and a catback as what that mod entails. they are talking about the entire intake and exhaust track, from filter, to piping, to throttle body, to intake manifold, to header, to cat, to muffler, to atmosphere. I didn't see anywhere where it said it was a 60hp gain though, but with a well engineered race inspired airflow design, you can accomplish a 20% increase in power.

most concept cars end as that, a concept. rarely do the parts used come out unless there is a sufficient market for them.
have you thought about an ser spec-v? the 2003 model comes with a brand new designed 6spd tranny and different engine internals, skyline inspired seats, lsd, 2.5l motor putting down 175hp and 180lbs/tq at the crank. plus it has a big aftermarket support. the 2004 comes with brembo 4 piston calipers up front. and it all comes in a handy and practical 4 door design.
so your requirements:
fast-high 14 second car stock
comfortable-you need to sit in those seats to understand
useful-4 doors and a big trunk
all for under 20K.