Full exhaust and you'll chop him dude!
The get a good boost controller to hold 12psi (elc holds better)...
I love s14 (series 2)s aswell, but atleast do your exhaust b4 u let the car go, r33s sound a HELL of alot nicer than an s14 does!!!
Power vs weight ratios, both cars will be similar with similar mods aswell, you wont loose anything with the skyline except the problem of the stock ECU not bein able to go past 12psi where as an s14 one can...
Hang onto the car until you've done the exhaust, you have to give it a chance, rb25s are awsome engines!