Rich fuel trim

1996 Toyota Camry 2.2l auto
No codes.
Timing 5 degree
vacuum is oscillating between 19.75-20 inhg ( some days it's steady at 21 inhg, and before the engine starting running rich it was 21.5 inhg)
.Idles and runs fine but Running rich in closed loop operating temperature

At idle 750 rpm St fuel trim in spec. Lt fuel trim (some days -8 but some days -25)

At 60 mph st in spec, lt (some days -8 , some days - 30)

Already replaced
Ect
Iat
Map
Throttle position
Upstream oxygen sensor
Air filter
Iac valve
Plugs, wires, cap, rotor, dizzy
Fuel pump, filter, pressure regulator and had injectors cleaned ( repair guy said injectors are not leaking down)

What else is there to try? Help appreciated . Thanks in advance

Fuel leaking past the regulator and into the regulator vacuum hose? I usually see that a lot more with Chevy products, but it's worth checking.

How's the downstream oxygen sensor? Reading rationally? In other words, if the upstream sensor is saying lean, does the downstream agree? If you disconnect the downstream, what do the fuel trims do?

No fuel leaking into regulator vacuum hose. The downstream is stuck at .115-.145 v, it's also stuck in pipe won't come out. If I disconnect downstream, the fuel trims stay the same they don't change at all

Can we move to the thread rich fuel trim ( what else is there to try). My phone had an error posting but somehow it posted anyway, now I have three threads about same thing. But thread I want to move to has more edit in post 1

It's getting horrible gas mileage. The upstream voltage oscillates between .1-.9 v (fast)

I'm not saying it's not there, but the oil level is normal and it doesn't smell. The exhaust doesn't stink either
There are no misfires

Tailpipe is black, and during the winter I could smell gas out exhaust but not in spring. No lab scope just obd2 scanner

Texas. The rear has been stuck for years even when the fuel trim was normal at 10 percent lean

You say no codes, idles and runs fine. So what is the customers complaint?

Have you verified that the O2 sensors are working correctly? If not drive the engine rich and lean and make sure they respond properly.

Have you verified that the fuel is good quality? What is the ethanol content in the tank?

What is the pattern regarding that different fuel trims (-8 -30). Go for a drive, graph fuel trim and O2 data between deceleration, medium load and WOT. Post the screenshot to here.

No codes. Complaint is it's running rich. I already verified o2 sensor are working correctly. Do not know ethanol content, I've tried gas from many stations.
Do not have graphing abilities, and can't take screenshot of laptop because of brightness being dim, can I manually write down the numbers instead

You haven't verified that the O2 sensors are working correctly because you said that the rear O2 sensor is pegged lean. At least one of them is giving incorrect information.
Dave.metz has suggested the correct next test. Put fuel into a vacuum hose to drive the engine rich and check your O2 signals or better still take it to a workshop that has a gas analyzer and get an actual lambda value to compare with what the ECM is showing.

I was told on another forum that the rear o2 sensor is only there to determine cat. Conv. Efficiency.

Is that what your trying to get me to do? Or ecm? Or wiring?

The rear o2 is defective, the upstream is good ( I've tried two new upstreams with same results)