I need information on a 1981 crown vic. 5.8L 351 winsor engin can you help me.

have u tried to run the car with the cats disconnected, u don't say why u replaced the cat's. Also what was the cylinder compression readings. how many miles on vehicle, has the timing been checked, could have a loose chain, also does the engine backfire

Try the fuel filter if its sluggish. Is it missing at all try a tune-up with plugs wires cap rotor button