There used to be something similar sold for Minis in the 60/70s.
Autocar did a proper test using a rolling road. They took a Mini, checked the points/plugs timing etc then fitted various economy/tuning devises. The one that disturbed the air flow did make an improvement, and actually got best buy, as it was also by far the cheapest.
But they then treated the Mini to new plugs & points and got an even better improvement.
This is a common mistake, people will often compare, say, brand new parabolics with the knackered leaf springs they've just replaced. Few people can afford to compare brand new bushes with brand new polybushes etc. I'm not saying these examples aren't improvements over standard, but often not as big an improvement as people think.