As you tell me, the problem could be your oil pump again, you put the original?, I have had several Passat Audi 1.8 turbo that the witness of low oil pressure is turned on, and changing the pump I have solved the problem, as the original is something expensive, my refacionist has been aware in Bruck brand and I have not had any problem, if you washed well, you have any moving noise. Changed the oil pressure hose that reaches the turbo, since it is very common that this hose is also covered and the turbo ends up, any problem you can mark my cell is 5518 447144, I am in the DF