P2002 00 Fault - Struggling to sus out

Hi Everyone,
Wondered if someone more experienced than myself could help me out.

Recently purchased a 2007 A5 3.0TDI Quattro and tbf its been nothing but a nightmare.

Noticed the car wasnt getting to temperature when i first drove it after purchasing. Replaced the EGR thermostat (was broken) but didnt fix the issue.
I then replaced the main thermostat and vwala 90 degrees in no time, great.

I then started to drive it a little but quickly had the P200200 fault, with the coil flashing light and the car in limp mode. I first did some motorway miles in a lower gear, didnt fix so i then did a forced DPF regen. Still the issue persisted.
I then checked the EGR valve and EGR cooler valve to make sure they were operating and both look to be working. Which look ok.
I then replaced the DPF diff pressure sensor and reset values on VCDS, but still no luck.

One thing i am not sure about looking at the fault codes.

Particul.filter diff.pressure: 23hPa (Anyone know what the usual range is for this figure?)

Exh t Adap TP Flt Us: -270.0 C (Anyone know what the hell this is? -270c seems a rather strange figure and i guess it would be related as its included in the fault data).

Any help would be really appreciated.

Many thanks to the forum already for the great database of help it is.