Have 4,2L with 125,000 miles. Check engine light is on with a P0171 code. When I first scanned the OBD2 there was two codes P0171 and P0174 codes. Changed spark plugs and wires along with a ETC sensor. Cleared codes and drove it few miles, light came back on and P0171 came up. System too Lean. I have great idle, no coolant loss. MPG has gone down. After the truck warms up I do hear a "ticking sound" could this be a intake manifold gasket? Or should i look at the EGR system?

 

Sounds exactly like what I had going on. I replaced the o2 sensors, intake manifold gasket and cleaned the MAF. It was the intake manifold gasket that solved my issue, the o2 sensors and MAF were just because I already had the truck apart.

You need something to read codes and show deeper information, it helps a lot. I have been using my sct x4 tuner to do everything plus custom tune it.

 

Yeah, I did find a vacuum leak on the rubber elbow under the upper intake. I did replace that. However there is a little voice in my head to just pull everything apart and replace all the gaskets.

 

If that took care of it you should be good. Replacing the upper manifold gaskets would not be that bad. The worst part for me was removing the lower intake manifold and fuel rail. No codes, no problem