90 Octane in any of the newer motors......Opti, ProXS, Yama, Rude.......pass say 2005 or so generate TOO much heat and will pop them like a tin can.....
BOOM goes the powerhead.
Later,
geo
90 wont hurt it, but theres no benefit to it either. actually it may lose a little power. probably not enough to notice though.90 is just more resistant to burning that 87.