Fuel consumption

My wife has already asked the question but now I have sorted the site out I can clarify things........ I had an F reg Range Rover with an " M & D fitted mazda SL 35 TD engine this was fantastic pulled a house and did 35 mpg last year I filled it up with top grade Petrol and ran it for 120 miles over three days ( went great !) on realising this I had pump and injectors checked all OK then MOT pointed out it would fail on body, so bought another RR G reg with 300tdi running gear which included high ratio transfer box The Mazda engine which every experienced person says sounds lovely has been put in and I have been struggling to get 22 mpg the turbo has been looked at along with the exhaust gate the tappets, filters , the boost pressure is now 14psi . I am running on larger tyres at 40psi and when I changed down to 125s made no difference ... Help I need power as towing heavy weight but economy when trundling on Mway. as it was ? Anyone know of a low mileage SL 35 TD ? thanks Pete

Sounds very much like injection timing to me. Perhaps from when you have had the pump set and refitted it. Retarded timing will result in worse fuel consumption , power and less noise. Are any of these additional parameters apparent?
regards
Edward