2000 f250 7.3. NEED HELP AND INPUT PLEASE

I was driving home one day and my engine just began to sound like it was knocking out of nowhere and rough idle at red light. Getting the rpm's up it seams to smooth out and noticed whitish smoke coming from exhaust every time I took off from a red light. So I ended up replacing the injectors and cups , valve cover gaskets, new harnesses, Also new high pressure oil lines as well. After cranking for a while it finally fired up and I let it idle for a while...during this time the engine was running rough shaking a bit and after 15 minutes of idle I revved it up and in high rpm it is smooth running. I know they say to drive it around for a bit of a trip before it will smooth out again but I noticed that there was oil dripping from the bottom seams of the muffler....small puddle of oil after 15 minutes of idle....what could cause this? ???