keep in mind that the throttle plate and shaft is a HUGE restriction in a throttle body.
2.5" pipe has a cross sectional flow area of 31.67cm square...
A 70mm throttle body has a cross sectional flow area of 38.48cm square..
However, the throttle shaft is on average about 0.5cm thick across the diameter of the throttle (0.5cm x 7cm) giving a reduction of 3.5cm square.. bringing the flow area down to 35cm square... a mere 3.33cm square increase over that of the intake pipes.. sounds like as close to a perfect match as you can get to me!
This is interesting, Ive never sat down and worked out the figures for mine
I run 3" pipes and 2 x 55mm throttles...
pipes are 45.36cm square
Each throttle is 23.75... x 2 = 47.5cm square. Man.. how perfect am I. Unintentional perfect match at that

Well not exactly.. because of those shafts. 0.4cm or so x 5.5cm x 2 throttles = a reduction of 4.4.. bringing the throttles down to 43cm square, 2cm square below the pipework
Oh well, neither are showing any sign of being anything close to their limit anyway

These twin throttles have the equivelant flow area of a 78mm (or so) throttle.
-Tristan