I should add, its in a defender, and is running on the last 50/ 50 SVO /DERV mix of the year. Fuel filter is under a yr old, oil and filter 1500 miles ago. There is no roughness at the upper rev range, and there isn't any black smoke etc. The actuator rod has not been tampered with, and the pump isn't turned up.
I have a gauge fitted and whereas it used to go up to 12 -14 psi, its now showing about 1.