Hi all, optimusprime, the part you are calling the push on cover for the plug is the suppressor. It is screwed onto the end of the plug wire with what looks like machine threads. I have seen some screw on type that look like a sheet metal screw and don't like that version. The wire on these engines is solid core metal wire if they are original wires. The suppressor ends are usually what goes bad and can be replaced without replacing the whole wire.
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The pliers are the tool used to crimp the end onto the wire but it is possible to use other types of wire crimp pliers and accomplish the same thing.
depending on how many ends you need to replace sometimes it's more cost effective to replace the whole set of wires. Just be sure to buy a quality wire kit. Bosch and Beru were the oem suppliers.
I hope this helps, Robert