Generally there is no difference between the CDT and the cars Labeled CDTi. anyone can buy a CDTI badge innit....
My own car has gone from a 116 to a 160 remap during my ownership, and the MPG hasn't altered worth mentioning, it is still 30 ish in built up areas, and mid fourties on motorways..
..
I suggest you have a problem on your latest car.....
...