2004 Mitsubishi Lancer Ralliart P0401

my check engine light came on so i hooked up my diagnostic tool and it read P0401, from there i looked up the meaning of that code and found this

Causes
A code P0401 most likely means one or more of the following has happened:

The DPFE (differential pressure feedback EGR) sensor is faulty and needs to be replaced
There is a blockage in the EGR (tube), most likely carbon buildup
The EGR valve is faulty
The EGR valve may not be opening due to a lack of vaccuum

Possible Solutions
In fixing this code, it is quite common for people to just replace the EGR valve only to have the OBD code return. The EGR valve is not always the culprit.

Use a vacuum pump and pull the EGR valve open while monitoring engine RPM's & DPFE voltage. There should be a noticable difference in RPM's with the EGR open
Clean out the EGR valve and/or tubing to remove deposits
Check the voltage at the DPFE, compare to specified values (refer to a repair manual for your specific model)
Replace the DPFE sensor (with a good quality / OEM one)
Replace the EGR valve

well all of this information is useful, i dont know where the EGR valve is to begin with, can anyone help me? How do i fix this problem safely
*I just purchased this vehicle about three months ago, last month, before i drove from Edmonton, AB to Vancouver BC and back i switched the car to synthetic oil and a higher octane fuel, premium usually 92 octane, could this be apart of the problem

not likely, I'd start with a manual purchase! My parts man's daughter has a Mitsu Lancer with an egr code and Im not sure what's been done to it but when he called Mitsu parts they said the valves aren't a common failure.

The most common problem for a P0401 is clogged egr passages. Once you find the egr valve apply vacuum to it while the motor is running and if the motor does not stall or run EXTREMELY rough then the passages are clogged. Also on top of the throttle body there should be some small vacuum lines some feed the egr control solenoid so make sure they are not clogged. (These lines should not produce vacuum untill the engine's rpm is raised)

I know this topic is old, but I wanted to comment that I had this exact same code on my Evo and it turned out to be a vacuum hose had popped off the EGR valve. I secured it back on with a zip tie, reset the ECU and it's been smooth sailing ever since. That might be something to look at also.