This 6' serial cable is exactly what you need to establish a solid link between your MegaSquirt unit and laptop computer. The cable features the required "straight-through" architecture as opposed to the "null-modem" configuration. It is long and robust enough to handle all your tuning needs.
If your laptop does not have a nine pin serial port, and only has USB ports, please purchase our MegaSquirt USB-serial converter instead:
Megasquirt USB-Serial Converter