NASHVILLE, Tenn. -- A nationwide investigation by the Channel 4 I-team found complaints about the 2007 Toyota Tacoma that included mysterious acceleration even when drivers said they hit the brakes. Channel 4 found a growing number of drivers who have had problems with the vehicle, which has prompted the National Highway Traffic Safety Administration to start conducting tests on the model. The former director of NHTSA told Channel 4 that the I-team has uncovered what may be "a safety defect of significant proportions." It's not easy for Frank Visconi to see what's left of his 2007 Toyota Tacoma. On June...