My question is why though?? I mean you gain a little horspower for the loss of torque!! Do you spend 90% of your driving in the 4400-6800 rpm range?? I know i dont...i hardly ever see that high unless im racing. I have the stock truck manifold on my 383 and it still gets 530 hp and 534 ft-lbs...this is from the Efi live dyno!! Also the same dyno i used when i had my 5.3 that made 331 hp and 375 ft-lbs