I believe the California version of the F4i does have an O2 sensor as does the 929 Ca version, but it is for all practical purposes worthless as it's range in the closed loop cycle is extremely limited & does not compensate for all external variables like a true closed loop Fi system.
A regular open loop sysem (49 state models) has no idea whatsoever that you have even put an exhaust on the bike & will not change anything to adapt to it.
The F4i is very rich from the factory so in all sincerity it will only get better as the freer flowing exhaust leans out the the mixture a little, but if you are really serious about your tuning then you need to get a PCIII or a PCIIIr & obtain a mapping created by an experienced dyno 250 tuner.
In fact you will find that the Powercommander alone will make a much more prominent change in the power delivery of your bike than an exhaust alone will. However they are best used together as a package.