Cross-over pipe on duals

No knowledge, but offer a few scraps. The first A-body 4 bbl V-8's used a single exhaust pipe that started before the tranny cross-over. They did have headers & collectors off the heads, as I recall. Apparently, the factory tested a full dual exhaust and found it performed worse, don't know if less max power or max torque.

When I owned a 1974 Honda 4 cyl motorcycle, the magazines were full of ads claiming 30% more power by installing their "4 into 1" exhausts. Finally, Honda and others started making the factory motorcycles that way and the same vendors seamlessy switched to advertising new individual exhaust pipes claiming "30% more power".

Perhaps H and X pipes are just eye candy, like rear disk brakes. Provide what people expect, though does seem like it would work. Next time a car rolls over in a NASCAR race, I'll try to notice if they use one. I am usually laughing at how completely non-stock they look underneath.