hi guy ! i am using seadoo RXT 215 2008years, below is my skis install after market racing parts list :

riva ECU
riva valve train kit
riva 50lb injector kit
riva open loop cooling kit
riva ride plate
riva pro-series o.p.a.s kit
oem reduction nozzle (size 83mm)
custom made power cooler
riva water box
custom made catch can
custom made 4" power filter
rude 2 supercharger impeller (rpm 8400 /14.5psi)
riva supercharger cluth washer
mc cluth spring washer
custom made RRFPR (setting on 60 psi)
riva 15/20r impeller
R&D aqu intake gate
seadoo rxt-t 2008 pump support

i install this parts , after i test the skis , my result is RPM 8400 E-TEMP 89F 74 MPH, i test riva solas 15/22r my result is RPM 8000 E-TEMP 90F 71.5 MPH , my friend using seadoo rxt-t 255 install and me same after market racing parts , but my friend skis can go RPM8520 E-TEMP 89 78.7MPH ,why my skis can no , loss 3-4mph , any pepole can ask me ???????