Trying to figure out what this electric harness goes to.

I was overseas at work. The wif turns the Disco into the local mechanic shop (we live in a small town). She wanted to figure out why the Disco was sluggish. Turns out the filter needed to be replaced. I asked her how much they planned to charge for the work. Came out to over $1,000.

So before I can tel her to get it back they start working on the truck. They drop the fuel tank. When they get the word that I would rather do it myself half the work had been done.

So I did some work for the rust in the last 1/3 of the frame. Trying to put everything back together. I can see where everything else plugs into but cannot find where this electrical harness goes.

If the pic doesn't post it is the only electrical harness the is located above the forward ffuel tank skid attachment plate (?) vicinity above the rear axle.

 

That's the connector for/to the fuel pump (that is mounted in the tank).
Skip to 9:35 and you will see where it plugs in >
OR just look at the 1st frame ( I didn't notice that).

 

Awesome, thanks. I have everything back together.

It has the same problem. Stuttering when the engine is running.
So this mechanic shop, which I personally do not like but my wife's family has known the owners for a long time, was wrong on the fuel filter being the problem.
Any guesses on what could be the issue?