Typically LEDs will only flicker if they are quite low on voltage or they have a bad ground. I assume your voltage is probably okay at the battery or you would be having starting issues. If the plug has lots of corrosion it could be creating resistance and a voltage drop there.

Are both tail lamps flickering? If so the problem may be on up past the cargo box. The wires to the tail lights should run together into a single harness which goes up and ties into the main harness. Inspect this connection to see if it's loose or corroded as well!

There's a plug if you continue to follow the tail light wires where they come up past the cargo box.

 

Corrosion isn't a factor . . . this thing is a week old. We haven't done much of anything with it yet. I just noticed it flickering the other day when my wife was driving and I was behind it. I unplugged the plug that is next to the muffler which brings the two harnesses together and plugs into the main. It seems to of cleared up I just wasn't sure why it was doing it in the first place. Plus, I am about to add some LED lights for backing up and a toggle. I didn't want the dealer thinking I screwed something up after adding that stuff.