Outer Limits 4x4 Board

Background:
Lost major fuel economy when i had my timing belt done.
Now I have the engine rebuilt, new injectors, turbo and pump rebuilt with boost aneroid; still haven't got my fuel economy back.
Mechanic said he has the engine advanced by 2degrees and will leave it that way for a few thousand Ks. He said it will retard itself a little as the belt wears in and then he will change the timing to factory setting later.

Question:
Do you think it is feasible that my old timing belt was just that worn in that it had retarded severely enough to allow me to get 750Ks per 65L tank compared to my current 500Ks per 65L

Vehicle: 91' D/Cab Hilux
Motor Model: 3L (2.8 litre diesel)

Hey mate if it ran ok and didnt do any damage (assuming rebuild was just gen wear) knock it back thats a lot of difference with the price of diesel.

A newly rebuilt motor may still be a bit tight and breaking in. As it wears in the economy may get better, but dinno if it will ge back the extra 150 Km per tank ...

Perhaps your injector timing etc needs looking at as well.

I wouldn't think a rebuild would lose that much economy. Having said that, just give it a coupla thousand ks but if it doesn't start to improve I'd be looking for something else. Pump timing possibly.

Rebuild didn't cause the problem it happened a while ago when i had the timing belt changed.
With the rebuild completely resetting everything i thought the economy might have come back but it hasn't yet