Originally Posted by Rod-Tarry

My Tuner Spec's my engine so if I open the bonnet & see a DV its because its required. Too many non-experts on here giving advice as is always the case.
My advice is never listen to advice on an internet Forum.

When I used a T4 about 700 years ago it had a DV fitted so it was required we ran 42psi back then. Another bit of advice you must not listen to is fit a DV & ditch the T4 it was outdated in about 1990.