How can i get more horse power

[Viper18876 at aol.com]

Hi I have a 97 200sx SE-R.  I took it to the track last year and ran a 16.3.
The site says i should be able to run it in  a 15.6.  What could be the
problem.  I have 2 1/2 inch piping from the cat back.  Exhaust and i short ram
intake.  I didn't understand when i ran I 16.3.   What else could I do to increase
horsepower.  I know someone who can do port and polish for pretty cheap if i
do get that how much hp with that give me and how are some other ways to get a
lot of hp.  Thanks