The absolute most fun per dollar mods that I have done to a zx (with turbo swap being the exception) have been to remove weight. It certainly will not hurt your gas mileage either. Loose the cat if you can, and aluminum 2.5" pipe yields a small power increase and drops 45 or 50 lbs. De-power the rack or swap to a rack if you have a recirculating ball, loose the A/C, power antenna, tag light, cruise control, small battery mounted on frame rail right next to the starter, LW flywheel. Include some misc brakets, bitchin betty, yata yata pretty soon you have a 2500-2600 lb GT Z with original safety, reliability, and comfort. And it hardly costs anything. Well maybe not comfort if you ditch the AC that's up to you. The aero of the zx is soooo much better than an s30, typically they lack some performance because they where so weighted down, but if you remove that weight...