THE PILOT OF A PIPER PA-46 ALLOWED THE AIRCRAFT TO STALL AND COLLIDE WITH THE RUNWAY, WHILE LANDING. HE STATED HE HAD SLOWED DOWN DURING THE APPROACH DUE TO PREVIOUS TRAFFIC STILL ON THE RUNWAY. THE AIRCRAFT WENT INTO A FULL STALL AND THE PILOT'S APPLICATION OF POWER WAS TOO LATE TO PREVENT A COLLISION WITH THE RUNWAY.