Sorry, but this is completely, totally incorrect. This misunderstanding arises from a fundamental mistake in understanding the way that a sound wave is magnified when it enters a resonating accoustic chamber, such as through the floorboard and into the interior of our cars. In certain frequency ranges, the entire inside of the car magnifies certain sound frequencies. It's an accoustic issue.
Change in tone and changes in volume are NOT, absolutely NOT the same thing as drone. Drone is a very irritating intrusion of narrow rpm, narrow frequency sound into the cabin of the car during crusing or when decelerating, which then combine with the accoustic resonance of the entire cabin to make the sound much louder than at rpms that are lower or higher. Our cars seem to form a highly effecient accoustic chamber that matches the frequency of the exhaust at approximately 2,500 rpm and a few hundred rpm on each side of that. There is a little drone left in the stock exhaust, although most has been tuned out with the stock CBE. But when you start opening up the flow upstream with the downpipe or the midpipe, this increases flow and drone goes up. This can be addressed easily and cheaply.
We can enjoy a healthy sounding exhaust, even raise the volume considerably and still avoid that cabin resonance that happens when the entire inside of the car becomes a resonant sound chamber for certain very narrow rpm bands with poorly tuned exhaust systems.
Carefully selected straight through resonators of the correct size and shape to attenuate the drone are the solution. Accoustic engineers can figure this out by measurement. We have to do this by trial and error. And done properly a good straight through reso will not change the overall volume or sound of the exhaust when you push the go pedal to the floor nor do they decrease power. But it can kill the headache producing drone at cruise or deceleration through the offending rpm range.
I solved my particular drone problem with a single very specifically selected reso welded into the middle of the race pipe for less than $100.
To OP: Try the test pipe. They are cheap. I don't know if it will create drone by itself. If it does, consider putting in a straight through reso in the test pipe or as close to it in the front section CBE as you can. A muffler shop can do this simple task very inexpensively.