How much street cred is too much? For executives at Mountain Dew, that may have been the question of the day on Monday, as the brand looked to move beyond a public relations embarrassment that had led it to end a multi-million-dollar endorsement deal with the rapper Lil Wayne. The brand severed its ties because of pressure brought by the family of Emmett Till, the African-American teenager whose 1955 torture and murder in Mississippi for supposedly whistling at a white woman helped foment the civil rights movement. The family took issue with vulgar lyrics referring to Till that were performed by Lil Wayne on a remix of 'Karate Chop,' by the rapper Future. In an interview with the Web site AllHipHop.com in April, the family said it would put pressure on the brand, which is part of the PepsiCo Americas Beverages division of PepsiCo, to drop the artist; Mountain Dew did so on Friday. Sarah Cunningham, a publicist for Lil Wayne, attributed the split to what she called ...