I put a Banks header on my 4 cylinder. Kind of expensive but it works well. I made several engined mods: cold air intake, larger throttle body, exhaust header and electric cooling fan conversion. Of those, the single best result was from the electric fan conversion. It took a big load off the engine. Do the header if that's what you want. It'll let the engine breathe better. You won't get much more hp, but it'll have better power delivery.