I have had cars remapped by RedDot before now as well, they seem to know their way around an alfa as well, as they kept begging me to let them map my GTA. the mad austrian guy there reckons he managed to get 250bhp out of a well modified 1.9jtdm GT before now as well, really knows what he is on about.
the 150bhp 1.9jtdm engines are good for about 200bhp if really pushed without any other real supporting mods.
its just a change of the cars computer software which usually means that they up the fuel pressure slightly along with the turbo boost to produce significant power gains on diesels. it usually brings about a gain in MPG as well, as the engine runs more efficiently.
my brother has his 1.6HDi Citroen C2 remapped (RedDot) and went from a standard 110bhp to 151bhp as well as gaining arounds 7mpg.
i know its certainly on my to-do list.