The MAF Sensor should read approximately the same displacement of the engine in grams, so 3.6 g for your 3.6L engine when it's idling. Clean it with MAF sensor cleaner and go from there.

https://youtu.be/Lf-KeFRAPZM Scotty addresses it here, around 2:30

You're right. You have a 3.6 L engine. Your MAF sensor should be reading closer to around 4 g/s at idle.

So let's take a step back and discuss how this works.

In almost all cases the driver controls how much air is entering the engine (by pressing down on the accelerator pedal). That opens the throttle plate on the throttle body and the more it opens, the more air enters the intake manifold.

The computer then adds the appropriate amount of fuel to that amount of air being measured by the MAF sensor.

So, the ideal (theoretical) air-fuel ratio for complete combustion is called the Stoichiometric air-fuel ratio. For a gasoline engine the stoichiometric air-fuel ratio is around 14.7:1.

That's what the computer (using the MAF sensor and upstream O2 sensors) is trying to do. It's trying to maintain that 14.7:1 air-fuel ratio on each cylinder bank of your engine to maintain complete combustion.

So simply put, the computer is pre-programed with air-fuel ratio tables. It "sees" how many g/s of air are being reported by the MAF sensor entering the intake manifold and it adjusts the length of the fuel injector pulses to provide the appropriate amount of fuel to maintain the 14.7:1 air-fuel ratio according to its pre-programed tables.

(Less air intake, shorter fuel injector pulses . More air intake, longer fuel injector pulses).

So when everything is working right, good cylinder compression, no vacuum leaks, no fuel delivery problems, all sensors working properly, these pre-programed air-fuel ratio tables keep the perfect (14.7:1) air-fuel ratio throughout all engine loads and rpms.

So now we get to fuel trims. 

The job of the upstream O2 sensors is to measure how well the computer's  pre-programed air-fuel ratio tables are performing by measuring the amount of unburnt oxygen (O2) in the exhaust gases and reporting those voltage signals to the computer.

In the instance that there is less unburnt oxygen present fuel will remain after combustion, which is referred to as a rich mixture. On the other hand, if there is more unburnt oxygen present it is referred to as a lean mixture. 

"Fuel trims" are the duration the computer must adjust the length of the fuel injector pulses which deviate from its pre-programed air-fuel ratio tables to maintain the 14.7:1 air-fuel ratio and fuel trims are measured in percentages.

So let's look at your individual case.

Your MAF sensor is reporting 8 g/s at idle. It should be closer to 4 g/s.

The computer's air-fuel ratio table will adjust the fuel injector pulse durations for 8 g/s of air intake. (the computer doesn't know the MAF sensor is lying)

But your upstream O2 sensors are measuring the unburnt oxygen in your exhaust gases and saying, "Hey, there's not enough oxygen here!" So the computer (evident from your Negative Fuel Trims seen on your scanner) has responded by reducing the amount of fuel to its pre-programed air-fuel mixture.

You tried cleaning your MAF sensor and are still seeing 7 to 8 g/s at idle.

 When we see Negative Fuel Trims we say. "you're running rich".

That isn't entirely accurate. It's more accurate in your case to say, "you WOULD be running rich if the computer wasn't correcting the problem".

The computer has already moved the negative fuel trim corrections to LTFT and they aren't anywhere near the limit of your computer to compensate for the problem.

So your computer is adjusting to maintain the 14.7:1 air-fuel mixture and you have complete combustion occurring with no driveability issues.

However, you may want to consider (after inspecting the wiring and connector) replacing your MAF sensor.

Yes it is. Give it a cleaning, check for intake vacuum leaks and measure again.

2017 Chevy Traverse Premier

3.6 FWD

85,000

I posted a question a while back about my MAF reading being around 8g/s at idle with a warm engine. 
It was suggested I clean the sensor. 

I cleaned the sensor and I’m still at around 8g/s. It fluctuates from low 7s to mid 8s at idle. Both LTFT banks are reading around -3 to -5. 

I have no drivability issues. No misfires. It seems my gas mileage is a bit worse. It’s a white car and I do notice the rear showing more exhaust “soot” when I wash it. Not covered in black but noticeable when I wash it. 

Could I have a failing MAF sensor? Im finding no air leaks and the air filter hasn’t been changed recently. I know the reading is high and want to catch any future problems this might cause. 

Thanks again?

May I ask: why exactly do you think that 7-8 g/s is a high MAF reading in your case? What were your MAF readings before you started thinking that you are having problems?
In other words: why do you think, that smth is wrong with with the MAF sensor or its readings,and not with smth else?
With higher-than-normal air consumption, your engine should be running rich = your banks shall be adding fuel to compensate for excessive air, while your banks are subtracting fuel.
Could not it be that the MAF sensor is OK and its readings are OK (adequate to the conditions you are having), but smth else forces the ECU into running lean? Like a faulty O2 sensor, or a faulty temperature sensor (which can also do it), or just a dying catalytic converter?

I was just looking at live data with my scan tool simply out of interest. I thought the MAF reading should be approximately the displacement of the engine. I posted that question here and I had a couple people tell me that 8g/s was high and made reference to the video where Scotty says the same. I cleaned my MAF but my reading is still 8g/s. 
Maybe one of the contributors who told me that my reading was his will respond.