Yes, as in RS-232 serial. USB/serial does not work with the A-300. The DashDyno you were looking into has its own connector, where the gizmo I bought interfaces with various flavors of PalmOS devices.
Since I have a Dodge, and no MAF, the device does not read MPG.
I am asking them about stuffing a couple formulas into the software to figure it out. It can't be rocket science since my overhead displays it...