The EGR valve is causing random misfires P0300. I first got the lean air mixture code P0741 a month ago. Two weeks ago the misfiring started.

No problem starting the cold engine but it struggles to upshift while accelerating. When idling the warm engine the misfires start up. Both of these symptoms are due to the lean mixture caused by the EGR flowing into the intake. Not knowing I had a defective EGR valve I first replaced both upstream O2 sensors. They had over 85,000 miles on them. That didn't solve the lean air mixture so I replaced my MAF, and TPS. I readjusted the TPS for days but still was getting misfires and lean mixture codes. I also checked my 6 year old IACV but it was clean and functioning. When the IACV was removed I could see that the EGR guide tube wasn't clogged. I cleaned that tube ~5,000 miles ago. I replaced the fuel filter while checking the fuel pressure which was fine. I checked for vacuum leaks but couldn't find anything leaking connected to the air intake system after the MAF.

Today I finally realized my EGR valve is gone.



As you can see this rusted valve is leaking. I tried pushing underneath the valve but it wouldn't move. Is the valve stuck open or closed? I presume it's stuck open causing the lean air mixture?

 

The vacuum tube connecting the top of the EGR valve and it's bypass valve has constant vacuum when idling. The FSM states the vacuum should only be present when revving 3000rpm. I unhooked the EGRC solenoid's connector but still received vacuum on that tube. I'll test the EGRC solenoid further tomorrow. Is the EGR bypass valve causing this constant vacuum?

 

While I don't know for sure, your guess that the valve is open makes sense.

You could install a new one, or remove and try to clean the one you have. Mine was a bit stiff. Don't recall what I used to free it up. Carb cleaner perhsps?