BYRON CENTER (WKZO) -- The conservative group Americans for Prosperity brought its anti-President Obama gas price promotion to west Michigan.  As they've done in other parts of the country, the group sold gasoline at a Marathon station in Byron Center for $1.84 per gallon, the average national price when President Obama was elected four years ago.  Everywhere they've done the event, AFP pays the difference to the gas station owner and limits it to the first 150 drivers.