Regarding the code definition...
http://www.kbmsystems.net/obd_fault_codes_ref.htm
P12xx is a code group for Fuel and Air Metering and Auxiliary Emission Controls codes. Porsche gets more specific with the 'xx' part.
Those generic scanners usually don't know Porsche specific codes.
I also have the Durametric software. It's pretty handy.
derb