Can't get rid of P0301 Cel
 

This cel P0301 is driving me crazy. I had one at about 84k. Replace the coil pack and all was good no problem. Now at about 138k I've got P0301. I replaced the coil pack with a brand new one I had just waiting for this problem to occur again. Cleared the cell came back on later that day. Figured I hadn't changed the plugs in awhile so I replaced all of my plugs with NGK6774. Gapped them to .051, car ran worse. Regapped them to .042 Car runs great now but I still have this damn cel. The other thing I have noticed when I start the car cold it holds steady at about 1500rpm for about 4 to 5 minutes before dropping to about 800-900rpm. Didn't know if this had something to do with it. I'm thinking at this point it is either cylinder one wire from coil pack to ecu or air/problem. If anyone has had similar problem any help would be great.

What is the correct gapping for NGK6774 plugs for our car?