I didn't know what to look out for when i first bought it to be honest.
The problems I've had to fix so far are -
he had the front higher than the back by a good inch or 2,
had the forge 007p installed as an atmospheric dump valve,
cut a hole in my bumper to suit the fmic, rather than hiding it behind the bumper,
hid a small cone filter inside the air box (smaller than the panel filter),
sheared a stud for an aftermarket downpipe he installed
and i'm sure theres more to come too