Zero:
I have had great luck with the addition of a Flowmaster exhaust on other vehicles. There are threads on mufflers.
Since I had the engine out of the rig to have other engine mods done, installation of the headers were done at that time. Increased HP and just as simple to intall as the original manifolds.
I have not heard another supercharged H2, but mine is loud all over the place, in and out and at all RPMs. Just the way I like it
Black Lingenfelter Lux