I am trying to determine whether my knock is a rod, a lifter, or a loud exhaust leak. I pulled the injectors 1 by 1 and on cylinder 4 the knock gets much louder with the injector unplugged. What does that tell me? Pulling the spark plug wires had little to no effect.

It is a constant knock/tapping noise that increases with rpm. Stethoscope points me to the passenger side rear, but it's loudest at the cat. That said, I can't feel any air and it's definitely louder than an exhaust leak normally is.

 

Big difference between a knock and a tap sound.
Which is it?
Tap is more valve train.
If the Cat has a broken sub-straight it can make a thumping sound.
If a rod bearing, pulling the injector changes the dynamics through the rod to crank clearance changing the sound due to a different pressure level.
Same type reaction should have been heard removing spark.
Your the one to sort it out.
Good luck.

 

No fuel, no power, noise still present. issue not in the bottom end