The story is... 98 4.0 ohv, throwing p0171 and p0174 both banks, both lean, changed MAF, still threw the codes, cleared em. Now the codes haven't been back but the truck has gotten progressively worse running and will not idle, lopes real bad. Fuel Pressure and filter in fine condition.

Then I replaced the upper intake (rubber ones) and the paper one below the fuel rail (lower??) as per on the sites. No change after that!! Haven't had the codes come back yet. I am stumped and i need to get back to work, any help/input appreciated. I have scoured for vaccum leaks and cannot find any. PCV or IAC maybe?? I just need another direction to go i am stumped.

I also replace the plugs and wires and no change either

 

Stretched, or jumped timing chain causing the cam to be out slightly?

 

Have you used a vacuum gage and checked your readings at idle? If so what were you getting?

 

did you replace the upper intake gasket?