[HO455]

Great to hear you found the problem. Thanks for keeping us posted on the progress.
I suggest you flush the fuel lines and tank. It may cure your cinnamon outbreak.
On your secondary throttle bore operation the lower butterfly's are mechanically operated but the upper ones are vacuum operated. The upper ones have adjustments to them that determine how soon they open. Engine displacement will make them open sooner (and faster) due to the physics of the volume of air flowing through the carburetor. The average 350 won't open them in the way a 454 will. Get your 350 to flow as much air as a stock 454 (not terribly difficult) and it too will sound like a demon from hell Hoovering up sinners.