newbie to quads..

I picked up a 2001 trailboss 325 4×2. It seems to run pretty well but it can always run better. It’s previous owner used it to pull his race car through the pits at the drag strip and I have used it to pull a few cars around the shop. It pulls well and does not seem to have any clutch or belt slippage. My question is are their any free or cheap mods that can be done to this to pick up a little power? I know its a small bike so to me its not really worth putting a bunch of money in but I don’t mind spending a little bit on it. I have some friends that have a 400 and a 500 polaris 4×4 bikes and we like to go ride trails and a little bit of light mudding when its to wet to go drag racing. I would like to have enough oomph to pull maybe a little bigger tires so I can some what keep up with them.

sorry for the story book but I hope someone can help me out a little bit.