well ive never seen a simonini 90 kit so i cant give you a dyno for it. but i dont think it will push out over 20hp. i might be wrong but i honestly dont think so. i kno people think 90cc is better than 77cc or 88cc but with the pro race and 44mm crank you wont be disapointed.
if u want to see the dyno of the stroker pro race vs. stock look at:
http://www.scooterbase.net/pics/22341/rs50.jpg