Just bought myself a 16 300 evo and im debating putting a flywheel weight on it or not. I've never used one before so some pros and cons/best weight to consider would be greatly appreciated.  

Are they not fitted as standard? When I tested the 2017 4t & 2t at Inch Perfect, John Lampkin said they were fitted to help find grip. 

Are you all ready using a slow throttle? You can always add another base gasket to the barrel.

I have no practical knowledge of flywheel weights, but thinking through the theory leaves me sceptical. While the weight will significantly increase the inertia of the moving parts of the engine, when you add in the weight of bike and rider it will be largely insignificant. Now someone, tell me I'm wrong.

The standard 300 has a flywheel weight fitted on the back of the flywheel (see picture of when we removed ours), so not easy to see unless you remove the flywheel. 

Some riders remove the weight to get faster response, so maybe ask the previous owner if they removed it.

I know. Barbers use the same trick, offering hair extensions to save them sweeping up.