Very basic i know but a DPF is designed in such a way that air doesn't easily flow through it as you'd expect.

I can't explain it very well but each segment in the DPF (inlet and outlet) aren't a continuous tunnel so to speak as this is what i was told and does make sense.

Its designed to block the soot/ash within it and the gasses ciruclte out via another square segment within the middle of the DPF but as it becomes blocked this process doesnt happen.

As i said this is very basic but explains why your air or water doesn't flow quickly through it.

I've spent hours cleaning one from a BMW X3 trying various chemicals, air and pressure washer's which eventually has started to work with a better water flow.

I don't know how true it is but i've been told a bottle or 2 of Forte advanced diesel treatment left to soak into a DPF by emptying it into the outlet end does help break up the ash followed by a good pressure was or ideally a steam clean.

With regards to live data,

I'm not actually sure that Snap-on does show any useful data about DPF pressure sensor activity in the specific model selection so your best to use expert mode then look through the measuring block sections.

If you can determine which channel number they are (ross-tech) then you can just do the same with snap-on in expert mode.

This si how i often use snap-on with VAG if the data isn't listed in the standard selection process.

thanks
lee