After you blew air through the drains did you run water over the area to see if any is still getting inside? If it is, I think the next thing to check would be the sunroof seal. Perhaps it has lost it's integrity, allowing water to enter.

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Mike Tangas
'73 280SEL 4.5 (9/72)- RIP
Only 8,173 units built from 5/71 thru 11/72

'02 CLK320 Cabriolet - wifey's mid-life crisis

2012 VW Jetta Sportwagon TDI...at least its a diesel

Non illegitemae carborundum.