I've not bothered with a powercommander simply because of cost. I have done the Kev Fuel mod, which certainly helps. Its relatively cheap, easy to fit and only took a week to arrive. Other things to try are removing the snorkel from the airbox and drilling some holes in the sides ( this is the Kev airbox mod ). Also check your cush drive as you mentioned previously that your chain has had it! You can pack the cush drive out with old innertube, believe me it makes quite a difference. When you have sorted your chain out make sure its not too slack! Good Luck.
Then when thats all done get a DNA stage 2 air filter.