Hi guys i have a FX140 2002 and i have

Pump Seal Kit, Solas Concord Impeller 12/18, Riva Intake Grate, R&D Velocity Stack kit, R&D Power Air Filter, Free Flow Exhaust
Soon a Rideplate...

I would like to know if the 12/18 will be fine for my jetski with all these mods.
or what else can i do to raise my speed a little bit, Should i use premium gas or regular gas ?