The air/fuel charge to the outer-most cylinders on a triple manifold with the end carbs not functioning will see increased turbulance from the "dummy" plenums, versus the stock intake.
Thus the end cylinders will run leaner.
This will certainly be measurable on a dyno. How much? Don't know. If you wish, try it. The loss will be greater at higher RPM's.
Personally, I would just do my homework, and run 3 carbs, but then I just like multiple carbs.
Jon.
