Engine knock on #1 piston any ideas

I have a 2003 dodge ram 2500 I purchased with a knock and I thought it was a bad injector. I removed the valve cover and started the truck and removed one wire from each injector one at a time. When I removed the wire from #1 piston the knock went away so I thought it was a bad injector. So I had a used 325hp injector and I changed the injector tip and but the injector in and still had the knock so I removed the injector and changed #1 and #2 and still have a knock in #1. The truck runs great does not smoke and has no blow by. Any help would be great

thanks