The hiss is apparently normal and nothing to worry about. It doesn't sound bad, there's no reason to complain about it really. The only concern was whether it was a leak, but even non-leaking exhausts have that sound.
As for rasp: compared to the stock exhaust, or say a mild exhaust on a big V8, there is some raspiness to the note. Mine was really bad at first, but that was due to a leak. With the leak fixed, I find the sound to be awesome. There's a little rasp in there, but it's just another subtle component of the sound, it's not a big fart can sound or anything.
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