Years Later Cos Quits?

Hey guys,
My truck has had roughly the same tune in it for years and years, a COS with extra fuel in boost and semi open loop. Lately I noticed it was down on power and the WBO2 didnt move much at idle. Scanned it, no semi open loop, only open loop, and when it hits boost it does not command or deliver a richer mixture.

What could change? O2s are reading what seems to be normal data, nothing was changed in the software for years. Only thing is the battery disconnected, did the COS get wiped out?

I'm just getting started with this one but I'm not even really sure what would change so maybe some of you older guys may have seen something? Thank you!

COS does not get wiped out.

Do you get any DTC's...?

What is rail pressure...? Do you have a manifold-referenced FPR...? Had fuel filter been replaced...?

Are you running MAF...? Is it clean...?

Is WB working ok...? Is it indicating rich or lean...?

I have more questions...