Weird question, but... Can you not leave a 996 unlocked?
I picked up a 2001 Carrera today and once I was done aimlessly joyriding in my new toy, I parked it in my garage with the windows down and doors unlocked as I have all of my past older (read: pre-1988) Porsches and went into the house. I came out not long later and noticed that there was a tiny yellowish light on in the roof-mounted courtesy light housing, as well as the frunk and engine cover button lights lit up near the driver's side door-sill. All other interior lights were off. I waited and waited but the lights never went off... it was only after I locked the car with the fob that those lights finally extinguished.
And that's when I discovered that the car had a motion sensor inside... reaching in the open window with the car fob-locked resulted in the alarm going off and nearly giving me a heart attack.
So now the car is fob-locked with the windows up in my garage.
All I wanted to do was park the car open to the air in the safety of my garage but it wasn't having it... so did I do something wrong?