Back to the oil issue for a sec:
This little leak caused my headliner to droop. Er, engine ... silencer, headliner, fire-retardant, stuff-thingy. I've now removed that.
At first I thought it was the vac line (the one w/the ziptie) that was causin' the problem (the one coated in sticky nasty thick oil); I guess I was blind at the time. I eventually wrapped a few things in papertowels and drove around for half an hour, trying to heat things, pressureize things, generally tear it up.
That helped me zero in on the cause.