I have a super turbo on my V6 Dakota and it has an annoying drone over 50 mph.

My Fury has a healthy 440, TTI headers, 3" exhaust, no cross over and Cherry Bomb Vortex mufflers. I am told it is really loud when followed, it can be heard over a mile away! However it is very comfortable when driving, you can easily hold a conversation at 70 mph with the top up or down. The Vortex mufflers have a very low restriction, slightly curved follow path, but the case is super thick and solid. They have a deep, rich, mellow sound, but they heavy case seems to help funnel all the noise out the back, rather than up through the body. The only insulation in my car is the jute carpet padding.

I have experienced the same results when I used to have iron manifolds and 40" long glass packs. My brother used to have 24" packs on a Duster that was awful, I have had 36" and 40" packs on a couple vehicles with great sound and no drone or cackle.

I think the thicker cases help the drone a lot. i wouldn't use the Vortex on something I raced though, they are heavy, not will never rust out!