Help Please 2.0 HDI

[Poodle]

That's pretty awful mpg, especially on the motorway, should be doing 55-60mpg at 70 on a motorway run. Worth a look at the maf imo, I don't know if you can test it the same way as the maf on a 306, might upset the ecu. I've got a feeling there's expected values for a healthy maf in the guide section somewhere, put yours on pp again and see if the figures tell you anything new.