I have had to have a lot of parts on my 2ltr diesel vrs, new injectors, HPFP, Lambda sensor. My mpg is quite down to about mid to low 40. When I purchased the car I was getting mid 50's. Does the car need to be put into Skoda or an independent company to sort out all the new parts to make sure all are performing as they should? Or does the car learn and just need to settle by itself. Any help would be appreciated. 

as well as parts has it been serviced recently?   air and fuel filter especially,    (even if not up to rec' mileage   for change=  too long)   a vag com scan wouldn't hurt either