DAF CF75 Adblue Problems. EURO 5 2009

Ok so it’s back on Derate.
FUMING :imp: to say the least.

Doing a little reading and see theres a fuel pressure valve that may be causing fuelling issues.
I remember the Davie saying fuel pressure is fluctuating slightly.

Now I have noticed some white smoke every now and then.
Could this be a thing?
Thanks