tuning boxes?

hi all
am new here but have been lurking for a while reading the useful guides
my names Andy from pembrey in west wales
have had my gen 7 celica about 6 weeks now and love it so far
however shortly after i got it it developed a niggly problem with the tickover
was ticking over at 1600 rpm when warm but thanks to the guides here i have cleaned the maf sensor and the throttle body and all seems to be good again as now ticking over at 800 rpm when warm :-)
i wanted to get my ecu remapped for a little more oomph(mines the 140 as i could not find a decent 190 anywhere localish)
was told that the ecu cannot be remapped???
so brings to my initial question
has anybody tried these so called tuning boxes?
have read mixed reviews about them so am curious as to the effectives of them
thanks in advance
this is the one in question