Ralph,
I don't use a pipe now, but back in the 70s and 80s when I did, we always put the pressure nipple right in the largest part of the pipe. Now I am not pressure or exhaust engineer, but it had something to do with the pulses of pressure that traveled down the pipe and back to the cylinder. And the pulse pressure at the largest part of the pipe, arrived and pressurized the tank at the crucial time for the timing of the engine.
That is what I remember from back then.
Frank