I assume from your car is a Z31 ? Honestly i don't know much about those. I do know about Z32's tho. You could set up any car to use a SDS injection system and you could probably tweek it to produce a lot of power but your average joe dosn't know or have the time to spend on a stand alone system. JWT is plug and play, safe in the hands of a novice and less intimidating. Here is what you mention in your post.

1) sds fuel injection ($800)
2) custom fuel rails ($100)
3) msd 72 lb injetors ($600)
4) JWT sport 600s ($2000)
5) bad-ass clutch ($500)
6) open exhaust (free)

What i don't understand is how you propose to tune a car without EGT or boost guages. Also 99 % of the people do not prefer to run an open exhaust. You also make no mention of cooling the intake charge by upgrading intercoolers.

While it is possible to temporarily make hp without good cooling it won't last long in the real world.

Harry