P0401 Insufficient Exhaust Flow 96 ranger 4 cyl

Read a lot of other posts regarding flow. Have some new info that doesn't match up with the solutions:
Got the P0401 code
Replaced the EGR - Schucks
Reset computer (battery disconnect) and code returned
Replaced the DPFE - Carquest
Reset computer (battery disconnect) and code returned
Checked hoses and EGR tube - all very clear
Applied ample vacuum to the new EGR while the truck was running and no idle change whatsoever
Removed EGR completely and checked exhaust port and intake manifold port with the truck running, both very clear. EGR exhaust supply was pressurized (and loud), intake manifold port at EGR had ample vacuum.
Next step is the EGR Solenoid but I'm getting sick of throwing $65 a shot blindly.
I removed the EGR Solenoid, hooked up a vacuum and applied a 12 volt signal, it rerouted the vacuum as it's supposed to to the EGR valve.
I've also applied vacuum to the vacuum hoses and no leaks.

What about the EGR flow sensor being bad and thinking it's not adequate when it actually is?

Any other ideas?

99.9% of the time a P0401 on a ford product is a bad DPFE and or restricted passages. You said if you open the valve manually the motor does not stall? If it didn't then the valve you installed is bad or the passages are restricted. But you said that with the engine running the intake side of the valve had vacuum right? This makes no sense. Aftermarket DPFE sensors are no good they are either bad out of the box or will go bad soon after. If you have a manual on this truck with the wiring diagram you can backprobe the return wire on the DPFE and measure the voltage with the engine running at idle it should be around .5 -.6 of a volt if the sensor is metal and around 1.00 volt if its the newer plastic one, as the valve opens the voltage should rise if all is ok.

At this point I'm wondering about just locking open the EGR valve, resetting the computer, and then trying to to pass DEQ emissions. It's strange that pulling off the EGR valve and physically plugging the egr intake manifold port and then unplugging it doesn't change the idle.

First of all that attempt is disabling an emissions system on a vehicle is illegal and very frowned upon. I've recommended blocking off egr's as a diagnostic step in the past but not as a permanent repair. Ascent is right jobber dpfe's are garbabe and your time would be better spent removing the throttle body and clearing the carbon from the passages and throttle body and iac etc and installing a Ford dpfe versus trying to cheat the test. Blocking the valve off or holding it open is still going to have an effect on the emissions from the tailpipe that will cause another gas to go too high or low anyway. no egr nox will go up, too much egr, vehicle runs too rich! I know you say the hoses, ports are clear but how have you determined this. applying the egr should stall the engine if not the ports are still pugged or you're new egr is junk, hooked up wrong etc.

If you have the valve off and the idle does not change at all,then the passage is restricted. Doing what you said about keeping the valve open will solve nothing because 1. the gases cannot be reburned because you have a problem with flow therefore the nox emissions will still be high 2. the PCM uses DPFE voltage to determine flow,if you have no flow then the voltage will not change so you will still have P0401.

Yeah, that's more frustration talking. I want to fix the problem not bandaid it. I'll check the dpfe voltage and just plan on returning it and get an OEM. In answering the questions:
"open the valve manually the motor does not stall?" Correct, visually checked that the valve was functioning with a manually applied vacuum.
"engine running the intake side of the valve had vacuum right?" Correct, a LOT of vacuum, almost sucked my finger inside of it.

Took it to the ford dealership.
They reported that the aftermarket DPFE is reading 1.2v when it should be between .8 and 1v. Acceptable but could cause issues later. An oem replacement is $180.
They also said that the intake manifold is needing cleaning for $300 and suggested to also do a fuel injection cleaning service for $100.
At this point I'm thinking of paying the ford dealer $90 for the diagnostic, taking the intake manifold off myself and cleaning it out. I still don't understand how it could be 'plugged' if the intake manifold has plenty of vacuum to darn near de-glove my finger at the egr valve port.
The other option is to give them $400 and tell them I want it to pass DEQ.

Thoughts?

Provided no other issues are created by removing the intake to clean it then it's likely going to only require a gasket set and your time. Im not sure the dealer has to remove it to clean it. It's either that or try the oe dpfe. None of the services they recommended are going to hurt the performance of the truck and if you're nervous of the undertaking leave it to the techs at the dealer.