Re: exhaust
No, I didn't remove any cats. Drone is a vibration (resonance) which occurs at certain engine speeds and is annoying. Engineers/physicists can give a more accurate description of the phenomenon.
The good news about my system is that, with a gypsy (off brand) muffler, the total cost was only $189 installed.
I'm not sure if it's related to the exhaust, but my mileage is consistently 23-25 mph in town.
Don