OLSD AFR slowly creeps rich at idle

I've got something going on with 2 trucks that is driving me crazy.
Both of them will slowly richen up at idle.
At first I was chasing my tail on the AFRs. If it was 10% rich I would change VE by 10% and it would over shoot. So I started adjusting ve by 50% of the corrections and it would still do the same thing.
So if it was 10% lean I would only add 3% fuel and it would be close.

But now I have the trucks idling with the hood raised and a 48" shop fan in front to keep them cool so the electric fans won't turn on and put a load on the engine.

They are still richening up. From commanded 15afr to 10afr over several minutes. ECT and IAT are stable.
I'm at a loss. I've tuned thousands of these trucks and never seen this.

Might have to look at all the fuel adder tables to see if one jumps out at you.

Thanks Joe!
I ended up going to COS3 so i can have IAT/ECT adders.
But when the ECT/IAT are stable, it is still richening up on me. :(

Is there anything mechanically out of the ordinary about these for you? Injectors that you trust? Intakes you've used in the past? Anything mechanical that can heat soak and cause this? What if you go for a drive and come back to an idle?

Nothing mechanical off.
Injectors are GM 36# Flex
I hate the chineseium alum sheet metal intake this truck has and heat soaks terrible under the hood of an S10.

After going COS3 and messing with the ECT/IAT fueling modifiers i think i have it under control now.


Ive got an 2006 silverado here now too that is doing weird fueling stuff in open loop.
Say at 60kpa and 800 rpms i can have fueling within 2%. Go for a drive and come back to the shop and let it idle and fueling will be 15% off with ECT/IAT being the same.
Ive used 4 different widebands and controllers to see if that made a difference.

Im not sure whats going on. Ive tuned thousands of cars/trucks and here recently open loop tuning is giving me fits.

Had one guy drop off a LS swap S10 and after a few weeks and having a couple other tuners remote in we gave up. I tried 3 sets of injectors, 3 widebands, 2 PCMS, and even had one guy remote in using HPT. I gave up and put a holley Terminator x max on the truck and it ran great hahaha go figure.