2003 Corolla stays above 10% fuel trim, unless throttle is more than 15%

Car is a 2003 Toyota Corolla LE with a 1zz-fe 1.8 liter engine with 150 thousand miles.

Prior to this, the car had an LTFT of 36% when engine load was at or near 60%.
Issue was resolved by replacing it with a new MAF sensor, that was exposed to directly sunlight for a long time.
The scan tool would show that the MAF sensor only detected 4.8 lb/min of air, instead of 6.8 lb/min of air, under load and driving at speeds of 60 mph.
Prior to this, I also cleaned the throttle body with MAF sensor cleaner and replace the intake manifold gasket which is notorious to fail on these 9th gen Toyota model.
I also sprayed 2 bottles of starter fluid all over the engine bay, and the STFT only went down when I sprayed around the air filter box that preecedes the MAF sensor.

Now, I'm worried the present issue of 10% LTFT will likely lead to a new CEL in the not so far future.

The 10% LTFT seems to only occur when car is idle.
I took the car for stroll, to obtain a correlation with other live stream data metrics.

While the car was stopped, in gear (not park), I pressed on the brake and gas pedal, to get throttle position and LTFT close as I could get them to intersect with each other with the scan tool's graph generator. LTFT came down from 10% to 8.5% and throttle position was at 15.3%; tp is 12% at idle.

I went back to live stream data and took a screenshot of all other data while TP and LTFT were 'intersected':

Edit : Forgot to include Engine RPM, sorry.



With the previous CEL that had a 36% long term fuel trim, I performed a vacuum pressure test in city located at sea level, on the following lines connected to the intake manifold:
Brake booster
Evap purge valve
PCV Valve

The pressure read 22 hg. This coincides with the spraying of starter fluid and not seeing any deviation on the STFT.
I performed a fuel pressure test, and got a value of 46 psi; after 30 minutes with engine offPSI was 40. Normal operating PSI with car on is 44 to 50. I also cleaned the fuel injector with carb-throttle cleaner, and replaced their micro filter (6x10.7mm). Also O2 sensor fluctuates between .075 to .750 volts, and its tip was placed in gasoline overnight, then sprayed with MAF sensor cleaner.

With fuel trim going down when opening the throttle body, this seems more consistent with a vacuum leak.

I would like to admit the new MAF is a non-Denso/non-OEM sensor, so build quality may be the cause of such result. Unfortunately I am tight with money right now.

The idler air control valve is something I've considered, but again this would coincide with the fuel trim increasing when throttle body is opened, as seen in Schrodinger's video. For Corolla, it's bolted directly under the throttle body. Idle RPM is 700.


Images depicting correlations of the graphs between 2 metrics, with superimposed texts:

Vehicle speed

Throttle position

Google converts 1lb/min to over 7gr/sec.
This is quite a feat for that little engine at idle. RPM is not in the data you shared, but I assume this data is at idle based on the rest of the post.