The problem with most short rams is that you pull in warmer, and usually dirtier, air from under the hood. I lost power with mine, because the intake air temperatures went up significantly (sometimes ~40-50 deg F higher in traffic). Look for a kit that would pull in fresh air from as far forward as possible. Better yet, consider a cold-air intake. You'd stand a chance of gaining some power and won't be cleaning/changing filters nearly as often.
Since your throttle is intentionally the bottleneck in the intake system, higher flow filters won't increase your mileage. If anything, pulling in slightly warmer air would reduce the fuel needed to mix with the less dense air. But that wouldn't be much, and it would be significantly worse if the ECU backs off the timing if the air is too hot.
+1. I was using a short ram intake for about 6-months and it was sucking in far too much hot engine bay heat. I considered making a divider out of sheet metal to block some of the heat, and even considered wrapping the intake pipe in heat reflective tape. I actually rigged up an aftermarket induction hose in hope of getting more air to the SRI, which sort of helped, but still wasn't getting sufficient cold air. In the end I decided to just make my own custom cold air intake.
All it took was two 125-degree 3" intercooler pipes, a couple of joiners and clamps, and a few hours of my time to cut the pipes and align everything properly. The pod filter now sits completely out of the engine bay, just in front of the wheel. The intake sound was slightly reduced due to the filter being further away, but the performance increased which is all that matters.
Here's some photos of my old set-up with the SRI and induction pipe that lead to the whole where the intake resonator box used to be:
http://carphotos.car...70054_large.jpg
http://carphotos.car...70055_large.jpg
And here's some photos after the CAI install (hadn't polished the pipes in these shots) -
http://carphotos.car...70058_large.jpg
http://carphotos.car...70059_large.jpg
http://carphotos.car...70061_large.jpg
http://carphotos.car...70060_large.jpg