Ok, this isn't a specific myth about a specific product. But how about the myth of power add-on'*...
So I bought this widget, good for 5 hp. Then this other good for 10 hp. Then another for 5 hp. All of these gadgets (legit or not, isn't the point) are bolted to my 240 hp L67, so I automatically now have 260hp.
I can't tell you how much this bugs me when I talk to my buddy with the impala SS. He'* never turned a wrench in his life, but swears he'* added 20 HP to his car, because the ads say so, and it would be illegal to advertise if it weren't true. This guys in law school too folks. Makes me worried he might get a job as a supreme court justice some day.
2000 SSEi; Silver, Grey interior
K&N filter, removed MAF Screen, TOG Headers, 3.4 Pulley, MSD Coils, Taylor wires, 180 Thermo, Pirelli P-Zero M&* tires, J.A.T.O. Booster in trunk