Based on comments on the UK 101 site there are no issues with the standard manifold on the 4.6. It would be nice to ditch the 101 exhaust manifolds and use the P38 ones but there is a bit of mucking around including cutting a bit out of the passenger side chassis to get them to fit.
Sure the carbied 4.6 does not produce the power of the injected version but it still produces a lot more power and torque than the 3.5 even with the 3.5 inlet and exhaust manifolds.
On the 101 the gearing provides enough oomph low down, it is in the mid to higher ranges that more go is needed as on the road the 101 is flat to the floor driving. The 4.6 provides the torque to make onroad driving a lot more flexible - not necessarily a lot faster at the top end but will hold speed on hills etc.
Garry

