Hello,

Same answer as above, this is generally caused by a bit of unburned fuel dripping into the combustion chamber. As Vin said this is not generally characteristic of a P-80.

In my experience it does not effect operation. On your next service I am sure they can clean it up. If it is bothering you I wouls send it in, but if it is running OK I would fly it until it needs other service.

Hope that helps,