I....   Honestly, a 2.25" pipe is plenty big so the reductions in area at the bends probably don't offer much restriction.  I think once the exhaust is past the intermediate pipes the main sources of restriction are past.

Hi Plainview... yes a very good discussion.

Just my opinion based on my research.... mandrel bends are considered by the exhaust systems experts a "measureable" difference over pressure bent pipe.  The first pressure bend is the restriction and doesn't matter what's after it.  There is more to the physics (flow dynamics) than just the restriction factor.. there is the turbulence and change in the velocity and sonic pressure wave caused by a pressure bent pipe.

Jumping on a highly touted camshaft profile with fractions of inches and very small degrees of change with the intent to increase volumetric efficiency then NOT completely considering the exhaust flow factor would seem like at the very least a badly overlooked design consideration.  In terms of economics and power gain, why would you spend $1200 for a ported head with OS valves and a torquey cam, then skimp on your exhaust pipe? 

How much more does it cost for 5 mandrel bends compared to the cost of 5 pressure bends?

Gnarls.