well you could just get free flowing dp and to the middle box, leave the rear box... not essential for stage 2.
yeah diff is 600quid and 600-700 labour
induction kit. go for either green or k&n, dont over oil the k&n though. 60-80quid
uprated dv is an uprated divertor valve(dump valve) forge 007p (searchy)
uprated tip is turbo inlet pipe again search and youll find loads of info on them
4 bar fpr is 4 bar fuel pressure regulator, 3 bar as standard, but some maps.. i.e revo require 4 bar.
now not 100% all this is right on the diesels.... have a trawl through the pm link i sent you mate, most of this will be covered in the guys readers ride... pretty exstensive list of mods on there.