Originally Posted by Matt

The OP is asking whether or not the addition of CAI to his Nismo would change his car enough to warrant (or need) a custom tune.

The Injen Nismo CAI aren't "tuned" for anything, it just fits the Nismo instead of the base. The ECU will still be programmed with the exact same tune as it was with the stock intakes.

To the OP, sorry, but I'm not an expert on tuning and A/F ratios and whatnot. Here is a link to Tony's (from F.I.) response in another thread:

The thread itself:
Intake, Header, HFC, CBE = Too Lean?

Tony's informative response:
Retune after intake/cbe/hfc


Others in the thread mentioned you may be ok not retuning if the only mod you have is the intake. Best thing appears to be deciding what mods you're going to do, completing them, and checking the A/F ratios afterwards to determine if you're in the optimum range or not.