I´m afraid i didn´t track down the tapping noise origin yet. After I changed the tensioner and the rails and the chain the noise was still the same. I´m waiting for spring time to set in at the moment so that its more comfortable to work outside. Once it´s warm outside I will take my Jag out and spend some time with finding the source of the noise. I have been listening a lot with my stetoscope and I´m pretty sure that the noise comes from one of the 4 front hydraulic compensators on the passenger side cylinder bank.
I´ll get back with more info.