Finally bought a Nismo intake, aka AEM brute force im pretty happy with how it drives now the stock setup appeared pretty restrictive. Next mods are walker b pipes and a gibson catback.
I had this setup but found that since I did a lot of town driving it sucks 180+ air from under the hood back into the ending. If you do mostly hwy driving you will be fine. I changed to a Volant that pulls air from the wheel well.
As far a performance it does seem to wake up the engine a bit. As for MPG I don't think there is anything you can buy to change that. If there was a engine tuner, which no one makes a good one, then maybe but it's as though these engines are programmed to only get 17 hwy and 12 city no matter what.