4k budget for a turbo kit piecing together will be hard. And instead of buying a turbo that has lag just for nitrous to be useful I'd just do something like a 30r and tune it then tune for spray on top of that.

Otherwise the nitrous will be useless.

You figure chris millers 1200hp hatch doesn't use nitrous to spool his big ass turbo. But I think it would be pretty bad ass nitrous&turbo together. But daaaaaaaaaamn it's gonna put a hurting on those internals.