I have a weber adjustable FPR as shown in the picture below. Can anyone confirm how you adjust it? I assume you loosen the nut and turn the Allen socket? Which way is increase/decrease?

Screw it in to increase pressure is the usual way.

Why have you gone for an adjustable one out of interest?

The ecoboost specifies a constant 55psi feed to the HP pump which is 3.8 bar. A 4 bar fixed would probably have been OK but wanted to stick to the spec.