after driving my car for a g few minutes it will lose all power on 2001 GMC Jimmy

and my gauges will go up and down. when i lose power i can have the gas pedal floored and it still loses power. I have replaced all my o2 sensors, distributor cap and rotor, ignition control module, ignition coil, idle air control module and new battery. some people say it could be the ecm or the crankshaft position sensor. the only thing the code reader say i have a misfire on cylinder 6. i can't even drive it cause it loses power so often.

by in Bay Saint Louis, MS on June 12, 2013
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2 answers
ANSWER by , June 12, 2013
Hook up a fuel pressure test gauge and drive it, see if pressure drops! Then see if pressure leaks down quickly when engine is switched off. May be a pump or fuel spider problem. Also possible catalyst broken in the cat. converter, hear any rattling noise? If you can't do these test have your mechanic take a look.
ANSWER by , June 13, 2013
poss fuel filter if it has one or low fuel pressure