Flowmasters are chambered mufflers all chambered mufflers will drone at highway speeds. Bassani is not a cambered muffler as far as I know. All mufflers other then Corsa will have a resonating noise at highway speeds but chambered mufflers are the worse
I have a Bassani catback and a Bassani X-pipe on my red GT. I wouldn't call it a drone, but the exhaust gets pretty loud around 80MPH with 3.08 gears. That's a little over 2K RPM. If you get the SS Bassani kit you can put baffles in the exhaust to drop the tone down.
i have 3.08 gears with equal length headers, dr gas x pipe and spintech prostreets and i have a lil bit of drone at 1700 rpm which is about 55-60 mph. at 2k rpm i can barely hear the exhaust at all.