How far to rev this 273 commando build

my set up is 2.5" - header collector diameter , 2.5" head pipes and 2.5" in and out ultraflos . This 273 commando makes more noise than my 402 stroker did with 3" to the axle. same muffler brand ultraflos. that was a 9.1 engine.......... 360 magnum crate with the RT heads . I think "compression" is what makes the exhaust sound so different between the two.