PPD TDI Injector Coking, Engine Codes BMN, BMR, BUY, BUZ (Solution)

PPD components with coking issues should be cleaned starting at a lambda value at full throttle of 1.40.

In the affected engines with PPD components, the injector nozzles become clogged, which prevents sufficient fuel from reaching the cylinders during injection.

The lambda value describes the ratio of air to fuel compared to a combustion-stoichiometric mixture (where all fuel molecules are completely burned with the oxygen in the combustion air).
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If the lambda value is high, it means there is a low amount of fuel relative to the amount of combustion air.
The values found for your engine are approximately 1.28 to 1.35 at full load in 4th gear. It's best if you explore the forums yourself or use the search function, as there's likely more information available on this topic. The lambda value can be displayed using VCDS.

If your average lambda value is 1.36, and "new/clean" values are 1.32, then you already have a performance loss of around 3%, which translates to approximately 5 horsepower with 170 horsepower.
Unfortunately, at higher speeds, smaller or clogged nozzle holes have a more significant effect than at lower speeds, which makes a reduced final velocity a plausible explanation.