TDI Engine Noise: 90 HP Performance

Hi!

A few questions about the TDI 90hp engine.
I've been driving a Golf IV Variant (manufactured in February 2002, with 7200 km on the odometer) with the aforementioned engine for the past week, and I've noticed that:
The engine becomes loud and rumbles at speeds around 2000 RPM.
2. When I accelerate, I hear a very high-pitched 'chirping' or 'singing' sound (easily noticeable at 60 km/h in third gear). It doesn't sound as consistent as the whistling of a turbocharger, but rather like a light, irregular organ-like noise.

I believe that the rumbling at 2000 RPM is probably normal for a TDI engine, but I'm not so sure about the second noise. However, I have to say that you need to pay attention to hear it. So, it's not very noticeable. But once you've smelled smoke , you become more sensitive to these things.

Please share your experiences.
Knilchi