For about six months the car has, I think, had two simultaneous faults.

1) A failed DPF regen about 1000 miles after a filter replacement.

The car had covered about 1000 miles since the replacement and had done about 100 miles of steady motorway driving on the day the DPF light came on. This time the fault was cleared by having the new filter flushed out.

2) When driving in top gear (usually on a motorway) the car would begin to lose speed, needing a change down a couple of gears before it would recover and pick up speed again. This even happened a few times before the filter replacement. Most recently this began to happen again but became more serious ending up in first gear barely able to move the car, although the engine would rev. freely the car would barely move. Struggled home and the next day it ran normally.

A diagnostic check indicated a possible faulty air mass sensor. This was replaced and the car has run normally for about one thousand miles so-far.

Could a faulty sensor have been preventing a DPF regen because I don't know now if the filter is being cleared and don't want to wait for a warning light to tell me it hasn't?

I do a lot of longer journeys, motorway stuff for about 40 miles at a time together with some shorter trips.

Had a 'data Logger' fitted for about 120 miles but nothing useful was recorded although the device reports different data on different vehicles. Would a different device more suitable for Mazda's do any different?