Help with poor fuel economy on 306 hdi

[scfc_151]

took my car in for a diagnostic and had a new battery, MAF sensor and fuel pressure regulator.

The car feels better than ever to drive, nice and smooth and feel like some of the power is back.

However, i usually got around 600-650 from a tank so I averaged 45mpg.

Now ive noticed when I brim the tank im getting around 500miles.

Ive checked that there are no fuel leaks, brakes binding etc and the car recently had a full service so what could the problem be?

Ive also noticed a high pitch whistling when driving at around 30-40mph.
This only happens when the revs are constant and goes when I accelerate or decelerate.

I dont know if this is related to the leaking intake manifold that I repaired in my last post

thanks

[Peter.N.]

See reply on 'Honest John'