Performance mods??

Have my son's 06 STS /ABS sitting there wanting some speed help. What is the "best" performance pipe to put on the '06 and keep the bags?-he uses it for work and transportation. Loud is not an issue. How about a K&N filter? I have a new one sitting there and am wondering if it will require a tune or if they even have any dealer installed performance tunes for these Sprints. How about Tune Boy set ups ?? Any ready to go??

What else is available to increased HP and Torque fairly cheaply and easily???

I feel the need for speed. Help appreciated! Thanks