Also if you find instead of oil, coolant,this calls for intake manifold replacement like mine. In front corner side rubber gasket getting old and starting to leak coolant, that goes in to the holes of plugs and causing misfire.I'm at 163k on my Gen 1. No injector issues. Just timing chain and turbo manifold. But I use top tier fuel so YMMV. It's not something I've heard mentioned frequently as being problematic on these engines. My misfires were plug gaps and the towel incident. I haven't even changed my coils.
Check the plug wells for oil too. The plastic valve covers leak eventually and oil will get into the well.