A6 AFB Engine: Hard Brake? Troubleshooting.

Hello,

I just drove my brother's car, as he claims that the brakes are very stiff and have relatively little brake assist.
I've also noticed this myself. Normally, when you press the pedal, it should give way slightly, and then the brakes should engage firmly without requiring much force.
From the beginning, these vehicles require more force to operate, and the pedal feels very stiff.
Could it be that the vacuum pump, which is mounted on the left cylinder head, is not providing enough power? The engine doesn't have a noticeable drop in power during slow acceleration, but when accelerating quickly, there's a slight surge around 3000 RPM, and the vehicle feels more responsive. I'm asking because the vacuum system is also related to the turbocharger pressure regulation. Perhaps this slight loss of power and the hard braking could be resolved by replacing the vacuum pump.
By the way: Has anyone ever had the vacuum pump fail on a V6-TDI engine? Best regards[/i]

I don't think the vacuum pump is going to be okay.
More likely, it's the vacuum hose for the BKV (boost control valve).
This is a typical Audi problem.
That would also explain the increase in thrust at 3000 rpm, as the thrust increases with increasing...
The speed and suction power of the vacuum pump increase.

alternative option:

Many models from the Volkswagen Group suffer from clogged water drainage channels in the expansion tank.
I've seen a few cases where people had to stay somewhere, and in some of those situations, the internal components of the BKV (presumably a piece of equipment) rusted.

I also thought that might be the case at the beginning.
Did I also experience the BKV (presumably a device or system) failing suddenly in my A3?
However, after that, the car was practically undrivable and impossible to brake, to the point that...
It almost felt criminal. At least the Poroesem hose has some brake reinforcement.