I have been searching everywhere for some extra ponys,
Best results from the 2.8 follow the same route as most other cars,
Rolling road remap.
For the 2.8 however, you can have either the 2.5 inlent manifold and throttle body or the dual vanos can use the 3.0 inlet manifold, supposed to get about 200bhp at the rear wheels.
I cannot find anyone to do the conversion in the UK. I have tried contacting Bmwsparepart in peterborough but not had any luck as yet.
they advertise the swap at £350 including remap.
If anyone knows of any reliable garages that do this sort of conversion please post a link.