I have what appears to be a leak in my roof. I have checked the drain in the sunroof and water goes right to the ground. We had a bad rain yesterday and today I got in and noticed the dark ring. When I touch it it appears slightly moist and sticky. I cannot find any pooling anywhere. Here are some pictures

 

With doors and windows all closed tight,put the blower on high, set air from outside, not recirculate, spray soapy water around the 3rd brake lite and see if ya get bubbles? If so there is your leak. need to get a new gasket for it. I made mine out of 3M 1/2" foam with one sticky side. hope this helps.