On that year 454 it is either leaky injectors or bad fuel pressure regulator. The original injectors leak down and flood the engine when hot. Buying new injectors of the same type will not help. You can either buy Lucas injectors new or Bosch injectors for the ford mustang used to fix this issue. Other than that you can live with it. I have a 2000 454 and so far I am living with it. If I ever need to take the plenum off I will buy the lucas set. They are about 325-350 for the set of 8. Also if the plenum ever comes off replace the fuel pressure regulator and check that distributor.