The best place to start is the exhaust; cat back, HFC/test pipe, and downpipe.
The stock air box with a K&N panel works very well. Your money will also reap more power with a boost controller than with an inake at this point.
A Mitsubishi metal/Evo IX BOV will go a long way for you and hold boost;
http://www.machevo.com/jdmevomrcoby.html
Tune it some how some way and...
