Update:

Just heard back from the service advisor that all drains are operating correctly and that they were unable to reproduce water entering the cabin via the sunroof, roof drains, windshield, or door. They suggested I bring it back in during the next rainstorm to see if this requires highway speeds and water on the roads to reproduce. Have to say I'm frustrated but I get it that sometimes these things require just the right amount of wind/pressure to occur. If that's the case I'd guess it to be a grommet but I find it hard to believe that much water would get through.

For now I'll crack open the carpet and continue to blow air under the carpet to dry it out completely. Have to laugh the forecast has nothing but sun the next 6 days! If I wanted a car that leaked I would have purchased a E46 convertible like my 03 M, that I knew would leak in one spot during heavy rain. It was a simple fix for that queen, don't drive it in the rain!

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'08 E70 3.0
'98 E36 M3 Convertible