The dyno I use is the same as RS Tunings. Only a few cars have achieved over 300bhp and there does seem to be quite a variation between seemingly identical cars.
My blue 350Z started at 258 at the fly, my silver one started at 285 - both on the same dyno with same wheels. They both gained about 25hp with spacer, decats and remap - as Mark says, more than that is difficult without major work.
Yeah I know matey, you have very good figures coming from your remaps. Ooop north seem to struggle for big gains. Don't know how accurate all dyno's are really but all you need to look at really is before and after