Having issues with P2195

I’ve been dealing with this code for far too long.
2015 Prius Two 293,000 miles
What’s been done in chasing it down:

Air fuel sensor, leaking exhaust manifold to converter gasket

Code returned with a no signal code as well

Checked wiring, took apart a/f plug to check wires and connections. All checked out good, adjusted the a/f sensor pins

Code returned, the no signal code gone

Engine began random misfire, code said cyl 1
Finally thought I found it, coil and plug are ok so replaced injector.

Misfire code gone, car runs better but P2195 returned

So pulled the intake, cleaned it, put in a new pcv valve, cleaned the maf and iat sensors, checked the intake for cracks and all the hose connections. The gasket was oil soaked so again figured I’d found the source. Put it all back together..

Code returned ‍♂️

Thoughts?

 

Update:
In going through all the diagnostic flow chart it was leaning towards the ECM/harness

Last effort was to just unplug stuff, even though they passed the check list

Started with the EGR since it’s showing it’s operating at +6 steps from where the computer wants it. More power, random bucking chugging still present, P2195 returned.

MAF disconnected, random bucking still present, P2195 returned

MAP disconnected, no bucking, missing chugging, 600 miles and no return of P2195

Replaced MAP and did a preventative replacement of the MAF, both from Toyota.

60 miles later that damn P2195 returned

Totally at a loss, guess I’m going to have to spend several hundred at Toyota for them to dig deep into the computer.

 

To answer, EGR hasn’t been cleaned, I have a new, well 15kmi, part to swap out eventually. But code returned with it eliminated.

Yes have checked for vac leaks

Car is on it’s 3rd Denso A/F sensor, the leaking manifold to converter gasket killed the heater circuit in 2, expensive lesson there