Oil in my vac lines?

[RB81]

It's income tax time and I'd like to fix the problems with my 92 240sx w/ redtop s13 SR20DET. It has what I believe to be bad main bearings and a bad clutch, due to leaking oil from a bad rear main seal. Aside from that, I've recently noticed it dies out when you take it out of gear or during lower RPM's, although at idle when you're sitting still it runs fine. I don't drive it much as of right now, and upon inspection today I noticed oil in my vac lines. Any idea what might be causing this?