I just wanted to let everyone know that I have got the problem resolved. What ended up being the problem was the new Motorcraft spark plugs that I got and installed wiggled themselves loose. This was causing a misfire/loss of compression. I got a different brand of plugs to try instead and they have 3 more threads on the spark plug and stay tight in the cylinder head.

So, people may want to be leary of putting the Motocraft SP-435 spark plugs from Autozone in their 1993 300 inline 6 cylinder engines.