On the pull truck engines we built for all the low end torque we could get, a set of equal length header pipes where each pipe held exactly the volume of one exhaust stroke made a measurable difference in torque during a dyno run. On the Super Stock Truck MOPAR 440 engine we ran for several years, each header pipe needed to be 8 feet long. I used a 6" diameter collector pipe and let the headers extend back into the collector to hide the extra length rather than just letting the pipes end at different points under the truck.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!