Ya, I have my 370hp 240. But I also wanted a good Mpg car so I just bought a 02 Sentra GXE 5sp. I seem to get around 35mpg which is what it's rated at.

Is there anything I can do to get better fuel economy? Will the SpecV intake add any fuel economy? Will it work on my car?

Haha, the Spec intake design is no different than your stock design, I believe. Sucks from the engine bay down to a resonator and back up to the throttle body, right?

Anyways, no, the Spec intake won't help you. A pop charger or CAI might. You could also consider (barring nasty puddles), and assuming that your intake is designed like I think it is, taking out the resonator and you'd end up sucking straight from behind the bumper, near the fender lining, just like CAIs, without the good filtration and larger piping.

You can get better mileage out of any car with simple stuff like intake and exhaust even. In fact, most bolt ons only help fuel economy.

I seem to get 34-37mph on the freeway, and 27-30mpg in the city. So i'm actually happy with it now. I guess i'll just keep it stock. Unless something can help a lot? The motor has a lot of low-end torque which I like, I'm afraid intake and/or exhaust might hurt that?

An intake should improve the midrange and won't really go either way on the bottom. From my experience with one, I've found that only the extreme low end (just above idle, 800-1000rpm) didn't seem to gain from it. As long as the intake is pulling a little air, it can fill up the piping real quick. Also consider the fact that the stock intake has a long, twisted mess of piping, this means that it takes a second to fill up anyway, so a shorter, more direct, but bigger pipe isn't going to change anything throttle-response/torque wise.

If you got a small-piped exhaust, you'd be fine. The stock piping is about 1 3/4in, so a 2 or 2 1/4 will not harm low end. The info you hear about big exhausts killing power isn't true. Most cars benefit, even N/A til above 2.5in. I run a 2.5in (room for header, high-flow cat, cams, and pulleys later on) and still don't feel a loss on the bottom (thought I have an SR20DE).

The QG18DE guys all say a 2.25 is fine, and the 2.5 does create a loss in power. Don't be afraid to try it, and if you feel a loss, trust me, you can offload a good quality exhaust without loosing your shirt with ease.

I say CAI (or even a pop-charger, that'd have good throttle response everywhere, but not much in the way of gains, mostly just noise and better filtration) and 2.25in exhaust (the BRM is nice , also consider Stromung and VRS).