Functionality of the turbocharger pressure control system in a 90hp TDI engine without variable turbine geometry (VTG)

Hello everyone,
Can someone explain how boost pressure is regulated in 90hp TDIs without a variable geometry turbocharger (VTG)?
Here's what I understand so far: the engine control unit measures the boost pressure. If this exceeds a certain value – approximately 0.9 bar – it must be reduced or kept constant (when using full throttle). Is some of the intake air simply vented at that moment? If so, where and how?
'In older TDIs, the hose used to measure pressure goes directly to the control unit. Is it still the same in the newer Golf 4 90PS TDI models, or is there a separate sensor somewhere in the tangle of hoses near the intake manifold? I haven't been able to find any lines where I could connect a pressure gauge to check the boost pressure.'

Regards,

Eike.

...in turbochargers with a wastegate, the pressure regulation works as follows:
- Depending on the design, the wastegate is a valve or flap that can be opened to divert exhaust gases from the exhaust manifold past the turbine wheel of the turbocharger directly into the exhaust system. In other words, it's a type of bypass that opens when the boost pressure is too high, thereby reducing the power driving the turbocharger.
In newer engines, the electric boost pressure sensor (which is often combined with an intake air temperature sensor) is usually located in the intake manifold.

Best regards, Rainer.