I see what you mean, but reading the Haynes manual for my car (found
here) and when explaining how the fuel injection system work, one section says:
"A turbocharger is fitted to increase engine efficiency by raising the pressure in the inlet manifold above atmospheric pressure. Instead of the air simply being sucked into the cylinders, it is forced in. Additional fuel is supplied by the injection pump in proportion to the increased air intake".
Note "Additional fuel". That's not quite what we want? BTW the Haynes manual mentions the compression ratio for this engine is 18.4:1 even though it is direct injection.
Thanks for your help, much appreciated!