rough idle with oil filler cap off
 

I have been reading about the AOS and the white smoke. My car is new to me and I have seen the puff.

So I just was out pulling radio and did the pressure test on cap. It was a little tight to start twisting but not much pressure. But the idle got rough and tried to smooth out, heard a vacuum like noise. Again very little suction but idle changed and heard air.

Is this normal.

Yes, it should run rough with the cap off since there is now a vacuum leak in the intake system.

To check the AOS, put your hand over the opening to seal it. You should feel just the slightest amount of vacuum.

If you run with the cap off long enough, it will throw a CEL, too.

Ok, I did not hold hand on but will do that in next couple of days. But from feeling of cap there will be very little. I thought that was normal with idle. New to Porsche so just being over careful.

Thanks