You can port the stock throttle body (I have to 66mm), but there are no swaps available. There is 2-3WHP to be gained from porting it (dyno proven). Also, you will have no gains from porting/port-matching/or polishing the stock intake manifold because the stock manifold allready flows well. Someone from another forum ported their entire manifold and actually LOST power, dyno proven (then again someone ported the lower manifold and said he "felt" gains).
If you want your TB ported, this is the guy that did it for me...
http://www.midpennmotorsports.com/
If you are on any other boards (thevboard.com or B15sentra.net) you can PM "Garland" he is the owner of MidPennMotorsports.
Hope this helps.
Also... here are some links for you.
Here is a link to the results of PORTING the TB...
http://www.midpennmotorsports.com/un.../portedtb.html
Direct link to the dyno results... (2-3WHP/TQ)
http://www.midpennmotorsports.com/universal/tbdyno.jpg