LC200 4.6L 1UR - Chasing Revs/Fuel Trim issue

[DirtyOptics]

Afternoon/Morning!
So, I have been chasing an issue with my cruiser since getting an airbox and exhaust put on.....In a nutshell, basically when in park, the vehicle will fluctuate revs between 580 - 700 revs.
I've hooked it up to techstream and can see the short term fuel trim values go pretty crazy and seems to be chasing a lean condition. I'll post a video below of the issue in action.



The vehicle is a Petrol LC200, 4.6L 1UR-FE. Only mods are a full manta exhaust/extractors, custom airbox/snorkel and a really basic tune from Warrtech in QLD, Australia.

I have tried the following without any changes:
1. Reverted back to stock airbox/piping.
2. Cleaned MAF
3. Throttle/Idle relearn
4. New intake gaskets (when I fixed the valley leak)
5. Tried to check for vacuum leaks best I could.

Things I am yet to try, but considering:
1. New AFS/O2 sensors
2. Fuel Filter/pump replace

Anything else I could try folks?

 

[DirtyOptics]

This is a run WOT, 3rd Gear up to 5000k RPM, to me the O2 sensor values seem ok, as do the Fuel Trims.

Then when in Park, we start to see something like this: