Wiring harness question... Black plug
 

I finally got a new harness, got it from all rotor... the wires that go into the smaller of the 2 plugs had other wires stripped in from maybe a previous boost controller install or something so I unwrapped the tape and soldered everything back up and re wrapped all the wires.

My question is in my car theres a black plug it comes from the body harness that goes into a small black box.

the harness I just received has this black plug on the engine harness...

So should I just plug the black box back into the body harness or should I connect it to the engine harness?

Also gotta pull the egr wire since I am using the pfc(was cut but I fixed it not knowing it was suppose to be cut)