Actually YES. You do need one. Trust me, I learned the hard way. You won't have any problems downloading the info to the programmer, but when it comes time to uploading back to the vehicle it's an absolute MUST. Trust me, lol, you need it. I was stranded in a parking garage until I got my hands on one.
I got one of these from Autozone
http://www.autozone.com/autozone/acc...mString=search
Basically you need a power source to keep your battery at a constant level, especially while sending info back to your ECU during a tune. Ask Omar at Velos, he can vouch for me on this. Good luck and enjoy your tune!