Scam? All??
I'm not allowed to post links yet, so: Google:
NASA - NPO 15715 - REDUCING SOOT IN DIESEL ENGINES
NASA - NPO 20219 - ELECTROSTATIC DISPERSION OF FUEL DROPS TO REDUCE SOOT
for a start.
The engine, and fuel injectors, are grounded, so it's no simple matter to charge fuel and keep it so, but it does seem to work..?
Electrically insulating a carburetor would be easy enough though and air boxes and inlets are generally plastic if one wanted to ionize the air... (YouTube)
ie: I think there's something here, but it's not as simple as copper and aluminum in your fuel fuel filter.