A record 19.3 million viewers tuned in to watch the Super Bowl champion Pittsburgh Steelers defeat the Miami Dolphins 28-17 Thursday, the fourth year since the NFL switched its schedule to begin on Thursday nights. NBC's first regular-season broadcast in eight years had a 12.6 household rating and a 21 share, Nielsen Media Research said Friday. It was the highest rating since the first NFL kickoff on network television in 2003 had a 12.9 rating.