Bolts, well, other than taking your money, most of them don't do a darn thing. The JAM bolt is a great little thing, it wont let you chop (after you wear it in, which is easy).
http://www.apbbolts.com/Spyder.html
Call them and ask which one will fit your piranha the best. You may have to loose a snap cocking system to go with one, but its worth it.
Other than that.... a decent regulator will keep it consistent, and possibly let you tune the pressure right.
Check here for upgrades for any STBB (Stacked tube Blow back) and how to tune them -
http://www.ottersccustoms.com/
Do realize that some tuning (like Low pressure conversions) will have you dump tons of money in for negligible results and a gun more prone to breakdown.
_________________
Later,
Bryan "Azzy" Spiegel
www.riversiderenegades.com
[url:3eidvjl2]http://www.PaintBallCity.org[/url:3eidvjl2]