I think you may find the 2000rpm spring is too stiff for you jezyg. I got the 3x spring pack from S.Assassins and tried all 3 at various tomes. The 1000rpm was good until i swapped out to a longer belt then the 1500rpm was better for me.
When i tried the 2000rpm spring with the stock belt it was actually slower uphills! Tested by goin up the same steep hill for all springs, i was around 20mph on stock, 26-27mph on 1000rpm, 26-28mph on 1500 (but was better up lower hills on 1500), dropped to 20mph on 2000rpm!
With a longer belt i only tried the 1000rpm i was using and the 1500rpm. 1000 was down to low 20's, 1500 took me back to high 20's.
For me in the past i ended up sticking with 1000rpm and 5.5g rollers, best all round set up for my scoot, decent acceleration, decent top speed and decent uphill ( at least compared to stock
) With the 1500 and 5.5g rollers it felt good and moee torquey but i felt i lost a bit top end, like i say 2000 was useless for me and turned my scoot into a dog.