Muscle, about your question... I did a test on an AEM CAI and a Stillen intake/Z-tube and got the same results (see the link in my previous post).

With that said, you can either go short ram or cold air, but before you do, a few things to consider...

Do you drive your car all year round? If so, does it snow by you? If the answer is yes to both, do not get a CAI. When I had my AEM, the salt, sludge, and snow killed my filter.

Another thing about the CAI is the slim danger of hydro-lock. If you drive through large puddles, you run the risk of submerging the filter, which can lead to water ingested by the engine - which is bad times. However, AEM and Nismo can be equiped with a water bypass valve.

Another thing about CAI's is the high end is nice, but the low end is not as good as a short-ram set-up (like a Stillen or Pop-charger).

MY $0.02:

Get a short ram. There are 3 alternatives:
Pop Charger (120-150 bucks)
Stillen (180-200 bucks)
K&N drop-in filter (50-60 bucks)
Also, get a Z-tube, the stock tube for the G's is not so great (70 bucks)

Exhaust...
If you have cash, Stillen dual cat-back ($1200).
If not, check out Borla ($780-850).

 

I just did an AEM cold air and its great, I'm sure INjen is great too.

 

Injen!! - Awesome sound!!