You will be alot better off by making some simple upgrades like exhaust and reeds. The 110cc kit is only going to get you to 103cc or so.
The 90 will perform much better with these upgrades rather than a bore kit.
Good luck. Feel free to email me if you have anymore questions about it.
Note: When chatting with these folks, do fully explain your wants, needs and riding conditions. They will match the proper performance parts for your needs.
For me, I went with a Big Bore and kept the factory pipe. Probably not the most efficient upgrade (for obtained power) but in my area, one must run a factory pipe. Noise level thing.
When installing a new pipe, many also recommend an upgraded CDI and Clutch Kit - at the same time. The clutch kit allows the engine to rev higher (tuned for the performance pipe) and the non restricted CDI allows the engine to rev higher then factory. For even more power gain, many also recommend an upgraded air filter (re: K&N, Unifilter or foam filter) to allow more air into the engine. The biggest air flow restriction on the Polaris 90 is its straw intake and restricted factory pipe.