Tightbore will upgrade the FPS, albeit only slightly but what it achieves is more consistency and accuracy.
How fast are you shooting now? What do you want to be getting?
Spring and maybe a motor (if your current one can't handle stronger springs).
Where are you located? Might help us to point you to who to talk to about upgrading (Read: We'll send you to a local gundoc).
ಠ_ಠLess QQ more Pew Pew
READY TO >> RACE