Please help me diagnose this 273

Most everything has been covered so I can't contribute much. I suspect a leaking intake manifold gasket from your original post. Vacuum leak from improper install of an aftermarket intake. Also just since it hasn't been mentioned the oil could be valve guide seals. It happened to me that way. The rest of the advice above was all pretty much spot on-good luck. It's a nice looking engine by the way compression test not withstanding-------------------you know-------------------