[A Cobra guy]

Well the good news is it's running much better. I replaced the exhaust manifold gasket on the left side. I'll wait until winter to do the right side unless it breaks up sooner.
I replaced all the wires on the left side and still have the older plugs in on that side. Dave & Max, you were right on about arcing. I have those foil covered heat sleeves on the wires for a couple of cylinders. Those wires are prone to hitting the headers. When I started it up there was arcing from the FOIL to the header. Moving the wire and the sleeve fixed that. I will put the new plugs back in 1 at a time to see if they are all OK.
I did re-do the compresion test. As oldguy instructed all plugs out and throtle held open. The block was cold. 5 cylinders were at 130 psi. 2 were at 120 psi. Cylinder no. 8 is only at 110.
For now I'm just going to drive it. If I have a great fall I'll get in another 750 miles before winter. I go through the car each winter and looking into whats going on with #8 will be on my list this year.

Thanks to all for the help, tips and education.