I'm looking at getting Banks torque tubes, they are a shorty style header. I have two questions will I need to retune? I already have a MBRP siso catback. And will it make my exhaust louder? I'm looking for a louder rumble throughout the rpm range.

 

No need to retune usually. Shorties don't move the stock O2 location and offer little power differences so no adjusting of a/f is needed. It will make it slightly louder because there is less material than the stock manifolds to adsorb sound. Keeping stock cats in place will keep the outside volume a little louder, but not terrible. The interior noise may go up a little more.