hard start/horrible acceleration

my 97 4.6L expy has this problem... difficult to start (like its not getting enough fuel) but when it starts it idles perfectly. if i slowly give it gas, it will rev up all the way like normal, but as soon as i push the pedal quickly it coughs and almost stalls (like it is starving for fuel). when in gear, i can only accelerate by very slowly giving it gas, and it will barely make it up hills. if i floor it , nothing happens it just coughs. converters, muffler, plugs, wires have been replaced. mass airflow sensor, fuel pressure, coils, and fuel filter are all good. all injectors are definetely working, im not sure if maybe they are clogged though? ive ran cleaner through them but no difference. engine code says misfire cyl 3, and one o2 sensor bad, but it has new plugs and idles great. any ideas????

check for vacuum leaks.

I think I have a leak just above the fuel tank. A hose that goes right above the fuel tank has a gash caused by another ring clamp. Can you buy jsut that hose, if so what is the size and length for my 2000 Expedition with a 4.6?

Thanks a lot.

Pull the vacuum hose from the fuel pressure regulator if it has gas in it replace the regulator. You can pinch off the rubber hose on the return line if you get power replace regulator. Otherwise do a pressure test as it sounds like a fuel problem.
Your bad oxygen sensor can lean down your fuel mixture. Also listen to the cylinder with the injector no.3
Check your in tank fuel pump. Disconnect it before the main pump. and put a coffee can under it. They only pump 3 or 4 psi but as they prime the big pump it will loose suction going up hill or on curves and cause hard starting if this pump is bad.