KA's like to breathe. One thing you can look into doing is doing a set of 1991 240SX SE exhaust cams ( naturally on the intake side retarded four degrees)
, a header, and a good exhaust system.

When you start helping the KA, you can get around 150 hp to the wheels. the intake manifold isn't that bad for the rev limit of the car, so there's no major upgrades there, but you can look into things like a larger throttlebody for some response, and what not.