Read the following post.
http://www.raptorforum.com/index.php/topic,5817.0.html
This will give you the instructions on how to set up the carbs correctly on the 660. This is not a normal description on how to install the jets, but rather on how to release some hidden horsepower on the raptor. It works for any setup, from a stock raptor to a modified raptor, running stock carbs.
I also mention some airbox mods you can do to improve airflow.
If you do just the carb mods you will pick up about 2 to 3 HP, and if you do airbox mods, you can pick up between 3 and 5 HP, even when using the stock pipe. Removing the baffle or muffler will also help to give you a bit more power, and you do need to jet the bike for these changes.
This is a proper , tested and proven modification, and you will love it.