Two weeks ago my Explorer displayed the code that bank 1 oxygen sensor was slow to respond (I forget the code #). I replaced the bank 1 sensor and disconnected the battery which reset the codes and forced the vehicle to relearn. Vehicle ran without throwing any code until I was entering a freeway at high acceleration. It now reads the codes PO401 (EGR Isufficient flow detected) and P1131 Lack of HO2S11 Switch-Sensor indicates Lean. I read that the vehicle is in open loop until the sensor reaches 600 degrees F and at WOT (wide open throttle). Entering the freeway I did not have the pedal to the floor but was trying to get up to 60mph from a stop. One note also is that I replaced the EGR valve about 10,000 miles ago.
Insufficient EGR is most often a bad DPFE sensor. The DPFE monitors the EGR valve to be sure it is working correctly, and sends a voltage from 1 volt at idle to 5 volts at maximum EGR to the computer, which then decides, based on the voltage, if the EGR is Ok. So the DPFE simply tattles on the EGR valve. However, when the DPFE fails, it does not send enough volts to the compuer. Computer then thinks "that dam* EGR is not doing what I told it to" and sets the insufficient EGR code,when in fact EGR valve is just fine. Its the DPFE that is fibbing. This is more likely in your case because of the newer EGR valve.
Nevertheless, you should probably do some checking before just swapping out the DPFE. They are about 80 bucks, and I suggest NAPA for the part. There are two small special high temperature hoses you will see below your EGR valve down by the exhaust manifold that run back to the DPFE sensor on the back of the intake manifold. Make sure they are connected. Some times they burn thru, and they can do lots of damage quickly if they fall off. Clean them out if you do the DPFE sensor. Different sizes, and the right connections matter.
Also, pull a vacuum on your EGR valve, make sure it holds it. With the engine running at idle, pull a vacuum on it, and it sould almost kill or will kill the engine.
There is an EGR solenoid under the upper intake manifold, and the EVR valve. Solenoid opens vacuum from the intake to the EGR system when computer tells it to, and the EVR actually applies vacuum to the EGR valve when the computer tells it to. They could be bad, but they are not common problems.
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