Remaps can royally mess up the lower speed/ rev regenerations, tis' true.
The exhaust shouldnt eject soot, ash, or unburnt fuel.
What this needs is a forced regen up on the ramps (near the door...extinguisher handy.... doors open..) whilst waving an infra red thermometer at the exhaust to see:
1) If the regen starts before the cat is hot enough
2) The temperature of the DPF and the cat during regen
The car can try (for a number of reasons) to regenerate too often, the EDC should recognise this and lock out further regenerations, but Examiner and compatable scan tools should be able to read this issue and suggest via fault code, whats wrong.
The filter isnt regnerated upon actual deltaP though, its done when the EDC has calculated through engine load, EG temp and other parameters when it might need done and it starts - the DeltaP sensor then measures if the regeneration is complete - it also has a high limit, so its the deltaP sensor that brings up the DPF fault on yoru dashboard.
If a tuner cant tell you this - dont use them.