OK you got me! These old eyes didn't bother to see the PCV valve on the other side just like you said. All I can think is that the tube is some sort of "re-breather" for the valve cover fumes.

 

I appreciate the help. So either way that hose shouldn't be the cause of my issue?

On my way home I'm going to grab a compression gauge so I can test my compression and thinking about buying a timing light as well because I remember someone mentioned I can advance the timing tj get a little more pep out of the engine.
As far as the spark plugs I believe they are still good. The tips are a little bit rounded which I don't think is good but it's not horrible. One spark plug did have quite a bit of oil on the threads. Is this something I should be worried about or is it ok?

 

Threads are fine. Oil on the electrode would have been an issue though.

 

So 90miata, how are things going with your issues?