I have had intermittent problems for year and half to two years. I get the P0505 code every so often, and the car runs crappy for a day once every two weeks or so. If it sits for the weekend then Monday it would run crappy until i drove for a bit. I was assuming it was a vacuum leak that i hadnt found yet. So, i was describing my issues with my buddy who is a BMW tech, and without hesitation, he stated that I had a leaky injector. Apparently it is a common problem among certain german vehicles. Due to the external vacuum pump we have, a traditional vacuum leak is harder to detect. Anyway, i was skeptical, but curious if he was right, so i dismantled the intakes and removed the fuel rail with the injectors. The pics below should illustrate what i found. needless to say, I called my buddy to tell him he was correct. Now i must repair the best i can until I can replace.