Doing a bit of Google'ing today and came across this guy, seems to specialise in tuning diesel's including Transits with or without turbo's, have a look at his site HERE, has alot of info on there
truck and driver magazine, this months issue has got a test on a new shape 3.5t transit lwb pitting it against a new shape sprinter its from a drivers point of view,they put the merc above it in terms of storage driver acceptance and scored it out of a 100,nice looking transit .