I haven't began to modify the X YET -- but I have a lot of experience modifying Nissan Z's.
I think you are on track to make gains in the stock ignition system. Hotter coil, better/larger wires, better plugs (stay w/ NGK), opened wider = better fuel combustion (increase hp and mpg). All factory systems are geared toward the middle of the performance spectrum. Nissan has a long history of improvability. One of the things that keeps me in their stable is that I CAN make it better, faster, stronger. They build a great engine to play with. Go for it. Post what you try (I know you will). If I get to mine soon, I'll post what I do...



------------------
Sean 'ZCaptain' Kester
Rockwall, TX
'01 Alpine Green XE 4X2 3Pack
'82 280ZX Coupe (modified)