Does the K&N filter model E-2990 fit in the air box or is it a open air cone type? I searched thier site and noticed that only the 200sx and 300zx is listed in thier high performance series. I have an '83zx N/A. What is the best air filter for this car for a fair price? I'm looking for things to do to get that little extra boost without major money....Other than intake and exhaust modifications, are thier anymore out there that can add a little more power?