Torque is very strong on my 1275 (Spot) it will pull 5th down to 40km/hr but to get it that low you need your foot on the brake...
Inlets are approx 24 - 25cm long OD of runners is approx 30mm or 24mm ID?
Plenum volume? I couldn't tell you it's a funny shape...
The manifold was made by a guy in Wollongong who specializes in these things...
It's a CG13DE but the bore and stroke are the same as a 1275 A series, at the same revs they should suck similar amounts of air however being 16v will make some difference.
More info here http://www.theminiforum.co.uk/forums/topic/253043-spot-the-micra-mini/page-4 including a dyno sheet (torque figures on the dyno sheet are weird I worked backwards from power and revs to find torque (in the build thread). Torque is similar to an A series but is there very low down and stays pretty constant.