performance question for 90 240sx

[90-240sx]

Right now the only thing my car has is an exhaust, headers that need to be changed, and a filter without the cold air system. What would be the simplest thing I could do to my car now for a quick hp boost and what price range am I looking at?

[benemorius]

Is your engine in good shape? Check the MAF, TPS, and various emissions systems for proper operation and ground. Check your engine and chassis grounds. Make sure to do a tuneup if you haven't already.

Aside from that: timing advance. Cost: none.