Could do a search for all this, but then no one else who is too embarrassed to ask will be any the wiser. I've been a mechanic for years, but have never really needed to know this info before.
i think its all to do with compressor housing size and size of the turbine, if its not ive been told wrong! mitch cheers for cd mate, good wids, shame about the manual was hoping to find all the information on turbos' in it, unless im not looking properly i cant find it!!! Steve thanks for the link, very usful information