Please Update whatever you do as I'd like to know what happens and your impression of the FWW and/or PV adj. You will eventually end up setting it back to stock with some time too. It comes in handy where I only have a short distance to pick up a lot of momentum and speed. Now with the weight on and 2 yrs riding behind me I have the PV set to stock. Look it up in your owner's manual and see what you can do. It WILL make a big difference if you want to tone it down and costs zilch. You can set it however you like and adjust it as you go. Both made the bike run a lot flatter for low rpm woods, less tiring with still plenty of grunt. I've had it set at zero tension and 45 deg clockwise. Mine was set stock at 90 deg clockwise from zero tension. It's an external adjustment and only take a few minutes to accomplish. If you really want to tone your bike down you can loosen up the preload spring on the powervalve (exhaust valve).
I guess because I'm a spode, don't race, and ride a lot of tight woods, it was a sensible mod to make for me. It's a nice addition and I would do it again. In that aspect it will help keep you going when you are gonna stall the engine on a long steep twisty hill that takes everything out of you. I can wheelie much easier now without it flipping over, I noticed that immedeately, And it will Lug down lower without stalling, but I'm either downshifting or feathering the clutch before I hit that point anyway. I put the 13 0z on my RM and it does make a difference, but not what I expected. You could also try some porting work by Eric Gorr, I think he can shape your power the way you want, but I personally have never tried it. You can change the powerband with pipe/silencer combos but I am running stock so I dont know which would be best. It will never be smooth like a ktm250 exc or anything but man it will rip on the straights when those wont. As for detuning the hit I am not sure the best way to do it. The bikes powerband will still be the same it will just be more controllable and tractible. There was nothing wrong with the 13oz at all I just went to the 11oz because it was what I originally wanted for the bike but was out of stock at the time. I have a GYTR flywheel weight on my YZ250. I only set the idle after the motor is hot, like after a moto session. It will also let you lug it a bit more without stalling as easily. I backed off the idle screw all the way, set my air screw (between 1/2 and 1 full turn) depending on conditions, and the slowly turned then idle adjustment screw until it would keep a low idle. What the weight will help is keeping rear tire from spinning up and trying to pass the front everytime you give it gas. But this bike WILL still have a huge amount of power in the woods. The 13oz weight is a nice smooth power delivery.