The crab intake with the whole sha-bang will run you about, well here is the site:
http://www.crabintakes.com/
Custom Exhaust ranges from $300 to $700, give or take. The GT-R is a dual out (not sure if there is a single) direct bolt on system (i think). Runs about $6-750 shipped (thats a roundabout price).
If your planning the tune go with the WHAMS tune. Not sure how much but if you search WHAMS on this site you'll find tons of info on this tune. Price est: $5-800.
As far as NOS: Cheapo:$400ish Good stuff: $700+
You can also delete the CAT or replace that with a high flow CAT. You could find someone to build you custom headers.
ADVICE ON THE TUNE:
Do the tune once all the performance mods are done cuz then the tune will be worthless if you add an intake so to say after the tune. Get everything done you want done first so they can tune the car right and get the most out of whatever you want like HP.
Of course, if you want to get down and dirty, rebuild the motor and replace as much parts as possible with high end performance parts and bore the cylinders out larger (3.5L to about 3.8 or 3.9 if you can get that much. the 3.9L could bore out to maybe 4.2L. Also, consider dumping $3,000 into the tranny cuz its a POS anyways and save yourself grief later.
Other than that idk what else.
