Just to add my 2 pence worth to this. BHM fitted a new manifold to my M16 last week and I am pretty impressed. There may be a placebo effect as the old manifold had sprung a leak and was blowing like a tractor but it feels like the car pulls much better and to slightly higher revs than before.
It certainly sounds a whole lot better with the exhaust exiting 100% from the back of the car too!
