Have a re-read gains arent 205 they are an improvement up to 205, a typical example would be a gain of 5bhp. My suggestion would be to look at the gains over standard, in this case 5bhp, then think anybody quoting above is potential figure inflation, Paul at RS Tuning is one of the best around, unfortunately for number chasers his dyno is a big ego deflator, ive felt it slap in the face a couple of times, but he is one of the few that will quote realistic numbers.
Imho dont expect big no. increases, a change in day to day feel of the car is the best you are going to get out of an n/a car