[mwebb]

not only do you want the column of gases in the exhaust to not be "impeding the flow of the next puff .
but you want the column to be accelerating away from the engine so that it pulls a very slight vacuum or at least reduced pressure to
assist the next puff so the the combustion chamber is emptied
more completely

in the automotive repair world -
it is thought that the speed of the pulses / puffs through the exhaust column is equal to the speed of sound .

so when measuring the exhaust pressure / vacuum pulse train
at the tailpipe

there is a delay = to the time it takes for the speed of sound to get through the length of the exhaust that must be factored in
when syncing the pressure / vacuum pulse train an event in the engine
like spark ,
when searching for misfire


except for the long line misfire this 4 cylinder engine is
putting out a uniform series of pressure / vacuum pulses at the load during the capture - many systems do not have clear delineated pressure / vacuum pulses
and instead they have just hash
like on any V6 engine with single exhaust and UNequal exhaust pipe lengths leading from the exhaust manifolds to the Y pipe where everything comes together

i SWAG the the Uniform pulses in the pressure / vacuum of the column of exhaust
is extremely critical for optimum exhaust efficiency