Help Identify this sound/problem
 

My truck started knocking after warming. Here are some before after vids. any ideas as to whats wrong. Also noticed intermittently dropping oil pressure.

While cold.


After warming.

That almost sounds like an exhaust leak. Warm it up and torque down the exhaust manifold bolts starting the in the center and working outwards. I don't have the torque specs, but a Haynes manual should be able to give you that info.

Probably there could be a problem with the rings or even the pistons. Does it guzzle up too much gas?

My truck does the same with the oil pressure light I think its just a bad sensor. Only gets screwy when its cold

Sounds like a piston slapping,