I think your best bet is to fab an aluminum (or whatever you like to work with) plenum. Looks like you have the room, and I would be surprised if you didn't see a decent performance increase.
Something like these:
http://www.google.ca/search?q=hayabusa% ... 24&bih=655 but built to fit in your space. The 4 runners into the plenum will give your engine more instant air giving better throttle response, and maybe give you cold air intake. Those cone filters aren't helping your power level at all.....
I would say there would be two easy ways to make a plenum for that car. Either way would be held to the TBs with small rubber hoses with clamps and the plenum would have an inlet on the front somewhere with a filter on it, or in the plenum.
1- take some short straight tube and go straight out from the TBs, and then bring the plenum over the top and make the plenum larger along the outer/bottom edge. The plenum would be curved to fit close to the bottom of the hood. These short runners would be better for HP gains. Really all you need is them long enough to get a hose clamp on them.
2 - take some mandrel bent 90 (or whatever angle you need to clear the hood and get lower) and then have the plenum be lower on the car. The longer runners should increase velocity and give you better torque.
Cheers.
Cory