Pressure is mounting for the Super Bowl-bound Kansas City Chiefs to end the popular tradition of fans breaking into a “war chant” while making a chopping hand motion designed to mimic the Native American tomahawk. A coalition of Native American groups has put up billboards in Kansas City to protest the Tomahawk Chop and Chiefs’ name. It’s also planning a protest outside Raymond James Stadium in Tampa, site of Sunday’s game against the Tampa Bay Buccaneers. The Chiefs made some changes in the fall, barring headdresses and war paint and making a subtle change to the chop. But advocates say it is not enough.