I had the same problem, only difference was my leak came from the sunroof cassette and it was not as severe as yours. I replaced the amp form iwantautoparts.com Its actually a website that Habberstad BMW started up to sell parts. They sell parts very cheap, cheaper than getbmwparts.com. As far as the connecter goes, BMW performed a "cleaning service" for the connector, which turned out to be a great success. Unfortunately, my radio problem came from the radio module, which dropped out channels randomly. Now my stereo is back to new.

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2005 BMW X5 3.0i
2013 BMW M3 Competition