Does your guy's motors have a real slight ticky sound like a sewing machine during idle. I noticed it when i was filling it up last night, it was cold out but the motor was warm, it doesnt sound bad it just sounds like ticky valves, but the motor is running fine, well it is basically new....i wonder if i am just being parinoid!
Opening the gas cap whith the engine running will not adversely affect anything. The fuel system is always under pressure (not vacuum) between the fuel pump and the injectors. The gas tank is outside the pressure circuit.