Now on the Fitch gizmo. Notice that power in the diesel went up by less than one percent, which is typical for different dyno runs. In other words, this is just another fuel magnet, maybe copper, or titanium, or platinum plated inside.
Putting a catalyst on the fuel line will oxidize some fuel molecules and turn them to solids (oxides) that will clog your fuel filter, or get into the injection pump/injectors.
If you think your fuel line magnet improved your mileage, go ahead and buy this one too (qoute:"I am seeing 30-35% savings" :-laf ) .
The only advantage may be with old gasoline, if it somehow prevents those varnish molecules from forming (I'm skeptical), but they publish no rosy user results for the diesels. Keep your $175.