You only need a USB cable and power supply if you're going to download custom tunes from the Diablosport site. It comes with (I think 6) "canned" tunes you can plug into your ECM right out of the box. Save yourself a trip to Radio Shack and get the U7778 USB interface kit right from Diablosport. It's like 30 bucks.It does need a USB to RS232 data cable (Radio Shack) and a 9V dongle/power supply (Radio Shack). The data cable to connect the tool to the data port on the car is attached to the tool.