Lifters making a lot of noise

Have the oil pressure checked.

First of all, this engine is a 5.7L 8 cylinder engine so the heading is a little off.

If the lifters are making noise then you will want to just go ahead and replace all of them while you are there. Main reason is, there is not a way to know how many are collapsed until you get it apart. So you just order a set of them and replace all of them.

As for the pin that is being referred too, that is called the latching pin and is only in the lifters for the cylinders that get "shutdown" during MDS (4 cylinder mode). Basically these lifters are latched so they no longer open the valves locking it closed so it traps air in the cylinder and as the piston comes up it compresses air and it creates a bit of a spring so the piston is pushed back down while it is in 4 cylinder mode.

Please see the attachments for more detail. Thanks