hesitation

I have 2000 5.4 that has a hesitation under accelaration or pulling on a slight grade. The engine starts to miss and trys to cut off. I have replaced the fuel filter, pump, o2 sensors and tps, cleaned egr and iac but no change. The only code I get is po420. Thanks.

P0420 is a catalyst inefficency code on bank one. This code is usually only a catalytic converter concern. It is possible it is a downstream 02 sensor, but usually we throw cats at it and it always fixes them. Unfortunately, catalytic converters are really pricey because they are chock full of metals like platinum and other synthetic and rare earth metals I can't pronounce, let alone spell. This could be causing your hesitation if your catalytic converter is plugged, or collapsed. The quick, fun and easy, yet loud way to see if this is your concern is to disconnect your y-pipe and run the vehicle and see if the hesitation has gone away. If it does, you need a cat, and they're around a grand and only come on the y-pipe assembly. Of course, if you like the open header roar, you could just run without exhaust but it would drive your eec system, the epa and local law enforcement crazy. Good luck with it and I hope I'm wrong, but it sounds like a cat to me.