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I’ve tried newer Diagbox installations (v7.x to v9.x), but they often cause communication issues with early 2000s ECUs or require too many resources on old XP/Vista laptops.
Conclusion
I know many of us are still working with older PSA vehicles (Peugeot 206, 307, Citroën Xsara, C5, etc.) that require or Lexia (v348–v400) — not the newer Diagbox versions.
I tried Diagbox 7.xx and 9.xx. It installs, but the "backward compatibility" mode just doesn't cut it for the really old stuff. The old native PP2000 interface is much snappier and more reliable for CAN 300/400 cars.