I've been running the car all morning flushing out oil from the coolant.
It's running an OLSD tune at the moment still set at 13.0 :1

Car starts at 10 and sits around 12.5 .

Occasionally when i've checked the temp, the AFR is around 15 then later back at 12.5.

It fluctuates about 0.5 point either side any way, but why should it decide to run leaner for a while.
It shouldn't move should it?

I think everything is turned off or shut down that's possible.

Any thoughts

'95 LT1 if it'snot in my sig.