Regarding 2 and 3...
How does an audio circuit producing destructive interference increase engine efficiency? Unless there is something I am misunderstood about engines a regular muffler only does that by using the exhaust shockwave to increase the compression in the engine. An electronic circuit with a speaker can't do that.
Personally, points 2 and 3 sounds like marketing BS to me. Where did you find them?
EDIT: It seems I mistook a tuned pipe for a muffeler.