K & N 57i - 57-0150 kit for 1.8 L silvia turbo

[PukkaSilvia]

i should imagine it has a small performance gain of maybe 1 -2hp over a regular induction filter. There more suitable to small normally aspirated hot hatches with crammed engine bays.For performance per pound its definately not worth the money.
A decent intercooler is the best thing you can do for the s12's intake system