From the reports I have read, the Dial-a-jet works as advertised. I'm thinking about puting one on my Griz because of the extreme temp changes I ride in up in North Dakota. 100+ and humid in the summer to -30 and dry in the winter.
Most of that power stuff doesn't have much effect on a stock motor. The best way to get the full potential out of a stock motor is with a pipe, air filter and re-jet. Also, if you haven't put one on yet, you need a clutch kit with those 27" tires. A lot of your power is getting lost in the stock clutch.