I have it and I am fixing to go buy some 20 inch. wheels.

Now i noticed that the attitude has a tire size change on it but will it change my speedo really? Or am i going to have to get a programmer for that?

Thanks.

it will not change your speedo on the truck. it will however read correctly on the Attitude display. In order for your speedo to read somewhat correct you'll need another programmer to do it.

Edge Attitude connects after the Computer.
You need a programmer to adjust your dash speedometer.