You need to check the drains on the sunroof. Unlike a lot of cars there are 4, 2 front 2 rear, assuming it is the same as the 944 then the filler tees into the sunroof drain on the O/S. Use a piece of stiff wire or an old speedo cable & ensure it goes all the way out.
Check the door seals, the tail gate seals & the sun roof seals. Ceck the drains on the tailgate latches. Is the tail gate tight, does it rattle ? If it does then the tailgate latches need replacement or adjusting. Check the rear light seals they let water in. Check the drains in the bottoms of the doors, they could be filling up.
And breathe!
Don't assume indies will automatically be cheaper than OPC, sometimes the Porsche price is better
