what is the difference between and aem intake and an injen?
(they make an aem intake for the g35 coupe right?)
and how much added hp would i get?

 

Here is some info from zchick.com There might be some information to help you.If the link won't work just cut and paste it into your address.
http://www.zchickz.com/cai2.htm

2003 Blk/Blk Premium w/navigation
Tinted Windows
Chrome Wheels
BRM Catback Exhaust
Injen CAI
Grounding Wires

 

they both have similar hp gains. the major difference is that the aem comes with a bypass valve to help prevent hydrolock.

from what I've heard the nismo intake is just a repainted and rebadged aem.

2003 G35 Coupe 6MT/Black/Graphite/15% tint/6 wire GroundingGear™

 

but the bypass makes you lose gains .. i have injen and i love it ..just dont go through puddles