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Let's assume I understand 2006 Volkswagen Passat GDI system as in with cam-driven HPFP and 65 volts boosted peak-and-hold solenoid injectors.

Based on 2006 2.0T Passat understanding what do diesel trucks use?

Do they have fully mechanical HPFP or does ECU play any role on HPFP control?
Do the all? Some? Many? Most? have "normal" 12v (or 24v?) high-z injectors or do they have peak-and-hold with boosted voltage injection?

Is there any technical difference between CRI and CRD or is it both the same https://en.wikipedia.org/wiki/Common_rail?

Short answer is "it varies"

Older stuff is purely mechanical, newer stuff has computer pressure control and injector firing.
Most new injectors are high-ish voltage piezo, and are fired multiple times per injection cycle.