Really Bad Knock (video included)
 

So I have a knock from my 01 F350 7.3 bone stock besides 6637 filter and 4" Turbo back exhaust. It started two days ago with a slight knock at start up. It would be faint at idle and thats about it. Yesterday, the knock got worse. I thought it was bad fuel, so I got a fresh tank of fuel and put in a small bottle of 2cycle oil in the tank. Didn't help. Now the knock is very loud at idle, and fades out when you give it a little throttle. It has a fresh oil change 300mi ago. Video attached below