??
I don't hear a hiss at all with non-resonated HFCs 18" resonators on the cans. I will say that cabin noise is now "beyond comfortable" and I'm ordering some more GTmat stuff to coat the interior to compensate. Girlfriend wore earplugs to/from a Christmas party on Sat night to passive-aggressively voice her displeasure.
My situation may be exacerbated since I ditched my spare and there's a big hollow space in the rear of the vehicle.
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