I have a 98 ford F150 that out of the blue came a sound on the pass side of the vehicle. I looked into it changed plugs, cop, a few rockers, and all lash adjusters. I have a YouTube video of my problem its making me sick hearing it. I rebuilt the engine top to bottom its a 2valve 5.4 no camphasers please help....

 

Broken manifold studs/bolts possibly since you mentioned you haven't done anything to the exhaust parts yet. Broken manifold studs/bolts are a common problem found on these trucks so is a leaky manifold.

 

Just tell people its got a diesel