You could just slap a turbo kit on it and it would be alittle faster.. Which Im thinkin about doing....
You could go all motor if you wanted to.. Get a z6 intake manifold, header, intake, exhaust, port n polish the head, maybe get some higher compression pistons, and sum other things like that.. Basic bolt ons and sum internals.. Using an ex tranny would be alittle better too because of the gear ratios.. You could always go bottle fed (aka nitrous) but thats all upto you on that one..
Now Ive heard that you can use a d16a6 non vtec aftermarket cam shafts in a b7 but not positive on that..