Car is definitely running rough at idle and the fuel trims, short term, are around 31% at idle, but normal at higher RPMs. I had a valve cover leak and replaced the valve cover gasket, hoping that would cure the lean condition, but it didn’t. Just through a code for bank one being lean, and the fuel trims are certainly showing it. Smoke test isn’t showing any leaks. I’m not sure where to look next. MAF’s were cleaned, O2 sensors are probably a bit old, but they seem to be fluctuating voltage wise correctly.

what can I try next? If the PCV valves were failing, wouldn’t they show smoke leaking through?

 

Mileage??? Did you replace the gasket(s) - there's multiple per valve cover or did you replace the entire assembly? Since the cover're plastic, it's best to replace the assembly, new gaskets can't compensate for plastic age/wear deformation.