I love my '09 300! Still!!!
I have done a few things to it that helped.
JD jetting kit
Extra rear wheel with a trials tire mounted for easy swaps from knobs>trials
2 teeth up on the rear
Mapping switch on the bars
Recluse Core EXP
Clear tank (3.1?)
Maybe a few other things that I can't remember, like shark fins and stuff.
This bike will rip in the desert and climb technical stuff all day.
I really can't think of anything else that will do what all the 300 will.
This bike is known for it's stump pulling torque and ability to chug without stalling.
If your bike is not pulling like a train at low revs, it is probably jetting and not the PV setting.
Try setting the PV back to stock and work on the jetting before you go all crazy with the spings and pre-load.
The maintenance is practically non-existant. I have around 200 hours on mine and have changed the plug once. Still on the stock piston and it has plenty of compression and makes no noise, so I'm not worried about that either.
The idea of swapping in a 6 sp has my interest and may do that next year.