Quote Originally Posted by Avalionis View Post
snip
It will sync your level, but if you have the gil you might as well walk into Ishgard and buy the starting item level 115 gear (alternatively, it may be cheaper on the market board depending on your server). This should give you an advantage even if it does level sync you because you will still be pretty well off in terms of stats.

I"m pretty sure you can do the fight at less than item level 90 though so don't fret if you're above that.