I also installed an ATS exhaust manifold when I did everthing else. HP and torque increased close to what Banks advertised. At hiway speed the exhaust sounds like a good turbo muffler on a gasser in the cab, more noise outside than stock especially under load. EGT dropped about 100* pulling the same hills as before, including the Grapevine. Very little difference in unloaded fuel mileage, about 1/2 mile more. About 3 mpg more towing. This is where the biggest difference is, will pull harder with less pedal.
Almost forgot, put a BHAF on at the same time.