Another vote here for the Slide hi-flow
When you say your car has "stock everything", does that include exhaust and intercooler?
To get the best bang for your buck and semi-decent results, you will at least need a turbo back exhaust and a bigger intercooler (front mount or maybe R34 sidemount), as well as some type of ECU (even a piggyback like an SAFC will get you bye).
$1K isn't going to cover it really, as you're looking at that kind of money just for the hi-flow. Cooler and exhaust if you shop around/buy second hand you can probably pick up for another ~$700, ~$200 for an SAFC, then installation (if you can't do it yourself) and tuning (~$200) on top of that.
This kind of setup on a lowish boost level (11 - 12psi) should see you around the 200rwkw mark, but a stock clutch isn't going to last long at that power level.
Fuel pump, AFM, injectors should be fine until you hit 220rwkw+