the Federal Trade Commission settled charges with SplitFire, Inc. in February 1997 regarding deceptive advertising.

 The FTC found claims regarding improved fuel economy, horsepower, and emissions for their "split electrode" spark plugs were false or unsubstantiated. 

the EPA's National Vehicle and Fuel Emissions Laboratory, which found no significant improvement.

https://www.ftc.gov/sites/default/files/documents/cases/1997/02/splitfir.pdf