Completely Lost

[Jasonaudio317]

Ok guys, Ive searched and searched and coming to a dead end. My 98 5.0 is throwing codes P0171 P0174 P0420 P0430. I have done several vaccuum leak test, replaced both upper and lower intake gaskets. The truck runs smooth, no hesitation, idles smooth, crisp throttle response, and plenty of power. Any ideas?

 

[FIND]

Have you checked your O2 sensors or the wiring to your O2 sensors?

You don't have a crack in your exhaust manifold do you?

 

[Jasonaudio317]

Ive checked 02 wiring, all looks good. my Ultragauge says I am getting good signal from my 02's, both bank 1 and 2 while driving. Smoke test says no leaks at manifolds, no cracks, or at least no leaking ones from best i can tell. Even replaced the PCV, might have cussed ford the entire time, but I replaced it

 

[RickOTR]

I would check all the small plastic vacuum hoses, there's a lot of them especially under the air cleaner and engine. It only takes a micro sized hole to cause the check engine light to come on, don't ask me how I know.