I had the same problem and even after blowing air down the sunroof openings from the top my carpet was still wet.
I crawled under the car with a piece of flexible hose attached to a blow gun and shot a blast of air back up the A/C condensation drain tubes (not the same as the sunroof drains). These are soft 3/8" diameter tubes on either side of the transmission about even with the shifter +/-. Took care of the problem when some chunks of organic matter flushed back out when I disrupted the clog.

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2001 x5 3.0 (sold with broken motor), 1990 e30 M3, 1991 318is, 2002 325i, 2008 335i Dinan stage 3 6 speed,