installing 8xl, Warrior 9920 in my e-maxx

[BrianG]

Removing the black jumper disables the BEC only. The red jumper is for programming. So, yes, remove the black jumper and leave it off.

Most ESCs these days require you to remove the red wire in the throttle cable some way or another, like in the diagram in your link. The BK warriors are one of the few that give you the ability to disable the BEC with a jumper so you don't need to remove the red wire in the throttle cable. It won't hurt anything if you do remove the red wire though.