Cat converter/light smoke from tailpipe

Check your cat, sometimes the heat shield mounts rust, the shield will rattle, if that's the case use super-long hose clamps to cinch it tight against the cat. 257k is some serious mileage, I would expect a couple of issues. Light smoke could be anything from worn valve seals or guides to rings. Probably a compression check is the first order of business, see what's going on there, something you can do, watch how the compression builds up in each successive crank, if cylinders are testing low, wet-test them by squirting a little oil in suspects, see what difference, if any it makes. Your mechanic will know what to do