More details I should of included .Pre-cleaned the voltage at the exhaust pressure sensor was 1.1v at idle hot, rising to 2.8v wide open throttle. This equated to 3 psi at idle up to 8 psi W.O.T.
After cleaning the DPF back pressure dropped down to 0.7v (1 psi) at idle and 2.0v (4.5 psi) W.O.T.
The report supplied from the cleaning service stated that the pressure dropped from 101 Mbar down to 43 Mbar and the flow rate from 100m/H up to 488 m/H.
The report also states the unit "cleaned well".
Sorry to use PSi, i find pressure is expressed in so many different units it becomes confusing with HPa, Kpa, M/bar, bar and Psi.
Post cleaning the max pressure on a stationary engine when flooring the pedal creates 4.5 Psi which is: 31 Kpa, 310 Hpa or 310 Mbar.