Who remapped it??? Could be a crap map mate, just injecting stupid amount of fuel?? 
It's either his driving style or there's an underlying issue
Think Kerrse has an R-Tech remap
If so its the same as Steve_PD's and he easily achieves over 500 miles to a tank; even with his dodgy pipework 
500+ is normally childs play, standard or not
Yes i have an r-tech remap and no dodgy pipework lol
Must be my driving style then

as far as i know my car is fine i have never got 500 miles out of a tank in 5 years, but then i never actually run it till the fuel light comes on.
Funny thing is i seem to get roughly the same mileage whether i go slow or fast lol