Just to make a point clear, i am not "tarring" re-mappers with the same brush, some re-mappers do a good job. unfortunately its the people who try and delete egr's and the like in the vain hope of fixing the vehicle in front of them which makes the re-map trade look rather shady.

To the re-mappers, could you diagnose a running fault on a vehicle with half (or more) live data pids missing/incorrect and trouble codes removed, with confidence in your diagnosis. In my opinion its almost impossible.