Exhaust sounds?

Yeah, most OE stuff is 409 or similar stainless, a lot of aftermarket the same(incl Dynomax,Magnaflow etc.). Unfortunately, predicting drone is tough, other than using a stock type muffler, all high-flow units will give some at a certain condition. Every eng/combo is unique, cam,ign,gears,pipe lengths...can all determine what RPM/load will cause that resonance. I like the Dynomax Super Turbos, but no SS option. & l've had a couple where the tubes loosened, or end-caps cracked where the flow-directors were welded. They are warranted, priced well, & last decent rust-wise.