The reason behind having the car back to standard is to then start a fresh new map, rather than trying to correct a bad map!
If the diagnostics have shown up nothing wrong with your car then either something like maf (it doesn't always throw up faults) or the guy still hasn't put back proper stock map.
Let mike check the map for you as he's offering.
At the end of the day us tuners do have access to databases of stock files and so should be able to find one for your car.
Personally I would just like to know that your car is giving you the mpg it used to get before even starting to remap it! Keep me posted