I've been chasing several issues on this truck for a while now. (Bank 1 Lean started it, replaced a lot doing that.) The most recent are the P0401 (EGR Flow Insufficient) code and the truck having a high engine speed between gears or after giving it gas while sitting static.

We just replaced the DPFE and the code came back after a couple days. Can't find any other leaks in the EGR system. Could the valve itself cause this code?

I'm not sure what the high ending speed between gears is from, other than the ECU not being able to correct for something else. The only parts I haven't replaced are the intake temperature sensor and the TPS.

 

P0401 code could be the EGR valve itself, the electrical connection. You can check the voltage/resistance of the circuit. You can find how to do this on the forum using the search link.
I had this problem 2 years ago and I changed both the DPFE and EGR valve. Now no more codes.
You should do the same.

 

I asked dad if he happened to clean the EGR valve when he had it apart. He said he cleaned the tube. I've got to pick up parts for my other truck, and I've replaced nearly everything on this one. Might as well throw another part at it.

 

Problem seems to have fixed itself...