Fouled spark plug on 92 Geo Metro 1.0

[nonewcars]

Been a couple of weeks since the last post. What I have found is the oil is blowing back out of the oil fill cap and slowly starting to cover the valve cover. So this tells me there is a lot of back pressure on the motor. Also discovered oil dripping under the car after dropping my kids off at school. Checked that out and the oil either came from the cam shaft seal or front seal. Oil was covered on the side of the oil pan and blown back against the firewall.

Would it be a possibility that the back pressure has been caused by the catalytic converted being partially plugged up? When I crank the car at idle, I get plenty of exhaust out of the tail pipe. But could there be some loose debris that as i drive it plugs it up?

Is it simple for a muffler shop to test the converter?

I know the pcv valve is good. I'm not getting any oil in the breather.