Reading several posts on here concerning 2.5TDI engine codes, it seems that the BAU coded plant is the one to have.

Why?

Is is simply that it's the final evolution of that particular motor, and therefore the one in which most of the wrinkles were ironed out, or is there more to it than that?

As it happens, the engine in my allroad is one of these objects of lust, and I wonder if I should be out there with a lint-free cotton cloth and a gentle finger, tenderly massaging its intimate places with warm Autosol rather than frittering time away on here.