Well I have it down to the 2 misfire codes. replacing the brake booster seemed to take care of the 171 code.I replaced the front 02 sensors, those I was worried that I might not be able to get out but they were actually pretty easy.I guess the things that I need to check would be the coil packs and possibly the injectors.

 

Well I have updated my replacement list.
lower intake manifold gasket.
plugs and wires
coil pack
both front upstream oxygen sensors
master brake booster
injectors on 3 and 4
egr valve
egr sensor
I took it to a guy with a nice computer (mogis I think ) who told me to change the egr stuff.He really did not know what else to do.I took it to a second guy with a snap on computer which did not say to much, he put a timing light around each plug wire and we could see that 3 and 4 were acting choppy he gave me a used ford coil pack and said to try this one I don't trust after the market ones. I have no logical place to go with this thing now,perhaps the wires leading to the coil pack or maybe where the wires are coming from are corroded.The truck is pretty clean looking. Perhaps a new wiring harness ,anybody ever change one of those before ? This thing is killing me in gas.

 

I picked up a used wiring harness at the local junk yard and installed it on my truck ,still misfiring.
Just goes to show ya, work yer butt off, throw lots of money at it, add countless hours.They say it is better to be lucky than good, remember there are 2 kinds of luck.

Thanks for all your help.

 

sorry to hear it bud. i hope you find the solution soon.

 

i had the same problem on a 01 4.2 took it to the dealer and found out it was the new ngk iridium plugs i put in they put in new motorcrap plugs and the problem went way. the dealer said they had problems with non motorcrap plugs causing misfiring.

 

have you changed the EGR Pressure Feedback Sensor?