Agree with above, i had a DTUK box on my A7, it ran fine for awhile then threw up engine warning light's and codes, cleared with CARISTA app.
Ran fine for awhile then started again, did this about 6 times over 4 months, i tryed all sorts, even as per DTUK advise when i rang them cleaned the boost control switch.
Eventually got fedup with it so sold it and got a remap.
YOUR mpg read out will be miles out with the DTUK box fitted, try a fuelly app for real world mpg..