1. 22" rear tires are a bad idea at the MX track and often 20" is bigger than you need. Most run 18 or 19 rear with a 19 or 20" front respectively. If it's badly rutted I've seen some run a 21/20 setup but not often and not in pro classes.
2. You shouldn't be bouncing off the rev limiter with only a slip on pipe, especially with stock gearing and big tires. If you are bounding off the limiter then you're not shifting when you should, you're making peak power somewhere around 7k rpm, not at the 9k rpm limiter.
3. What gear are you running in aorund the track? You should be using them all, at least 1-4, in order to get around the track the fastest. Normally to do this people have to shorten their gears and go with a higher ratio, not go to a lower ratio as would happen with the 14 tooth front.
Also, adding another link to your chain won't help you get the axle back farther if you're already at the end of your carrier adjustment.
And going up a tooth in the front, whether it's from 12 to 13 or 13 to 14 will have a noticeable affect on your "seat of the pants" torque. You may still have enough for your application but it'll be cut down significantly.