Engine Performance problem
2004 Cadillac Deville V8 Front Wheel Drive Automatic 120000 miles

I have a 2004 Cadillac deville that has the P0300 code and flashing check engine light on it was missing and sputtering. I narrowed it down to what I thought was spark plugs and 2 bad coils, changed them and it helped for awhile (about two miles). Now it is missing again and has the flashing check engine light and po300 code again I checked for vacuum leaks and didnt find any. I checked for bad connections and didnt find any. I checked the EGR valve to see if it was stuck or blocked and it is fine also. and the exhaust smells rich, but not like rotten eggs. I also had a new fuel pump and filters installed about 6000 miles ago. I also narrowed it down to cylinder #7 on the scan tool and the cylinder seems to be dead and completlely misfiring, I then swapped fuel injectors on #7 with 6 and #7 still is misfiring. I put a new ignition coil on # 7 cylinder also. I also checked compression and it was fine. I checked for spark and it was good, Any Ideas? Ignition module? Crank sensor? Cam sensor? Bad wiring harness? It is running very rich also.