I'll bet the drag is still not up to... say a G35 with a Cd. of .26-.27. The G-Nose does make the car alot more slippery though. From what I've read, a stock S30 has Cd. of about .46. Being lowered, dropping the nose, as well as covering the headlamps would help considerably, but the S30's aero-faults also lie in the windshield's rake and curvature, as well as an exposed underbody. A few underbody panels would REALLY make that car cut through the wind, but another problem is found in the sudden bulge of those fender flares.
But, I'm not an aerodynamicist, so what the hell do I know. I could be totally wrong.