[thstone]

P0410 and P1411 are SAI issues. Those don't typically affect start up.

P1420 isn't listed in the Bentley Boxster repair manual.

P0420 means the catalytic converter isn't working properly. This can be the cat itself, the O2 sensor, or the wiring.

To my thinking, I don't think that any of these would cause a hard start problem. The SAI only affects emissions at cold start and the cat/O2 sensors aren't part of the system until the ECU goes into closed loop operation after startup.

With that being said, the obvious place to begin troubleshooting is to correct all of the obvious faults/codes and then go from there...