I have a misfire in Cylinder 6 but when I start my truck up and it makes a loud Clank noise that sounds like it's coming from the intake.
Thank you for writing in. Your insight about hearing the sound coming from the intake may not be far from the truth. It is possible for the intake manifold to fail, allowing a leak to form next to cylinder 6, and also effecting components in the area. This would explain the sounds, the misfire, and likely some of the running problems you may be experiencing as well.
However, you want to make sure that you check the spark plugs, the spark plug wires, and check for signs of spark plug fouling before you start to look into more serious issues. You may also want to run a compression test. Good luck!