Diagnosis Needed

[user456]

About a week and a half ago, I purchased an Explorer Sport Trac (2001). Previous owner said it "ran fine" the last time he drove it. I'm skeptical.

Idles rough (will stall in park, drive and reverse)
Put a new EGR valve on
New Throttle Position Sensor
New spark plugs
Running lean
Has thrown code p0171
Check engine light was staying on prior to new spark plugs being put on. After new plugs, check engine light is flashing.
Some plugs' insulator was red, others were charcoal black.
Considering trying an AIC
Odd clunking/gluggling sound coming from air filter area but filter is clean
New MAF sensor
Performed a smoke test, couldn't find any leaks other than the throttle position sensor and EGR.

I'm at a loss. Someone please help diagnose this thing.

 

[410Fortune]

Running lean indicates low fuel pressure
Or intake gasket leaks

If the intake plenum o rings have never been done… it needs them

If it runs worse after new spark plugs you need to check the wires and firing order, basically check your work

Fuel pressure test is needed