P0171 Mitsubishi -

Question

hard to start after filling up the gas tank.

Answer 1

The symptom indicates a problem with the purge control valve being stuck open. This usually would cause a rich fuel mixture, not a lean one and not on a specific bank.

I would disconnect the purge control valve, clear the code and drive it. Also, since it's only running lean on bank 1, it's possible the front O2 sensor on bank 1 might have an issue.