Newbie with some questions

[trukki81]

Hi,
New to the sight. Im possibly interested in purchasing a programmer, and thought I would sign up here and try to learn some more about them.
I know what they do, I just dont know how they work and im not quite sure if I should purchase one.
My truck is an 05 F-150 FX4 5.4 liter with 31,000 miles. It has a K&N CAI, and a Stillen muffler, and it runs great. Im just curious as to what a programmer can do for my trucks performance? From reading some posts, it seems that some people experience problems, or they are not completely satisfied with the performance, and others are tickled pink. I have mixed feelings about making a purchase. I dont want to buy a $400-dollar headache.

I appreciate any and all feedback
Thanks