It goes from the rearmost head bolt to the firewall. It's there to suppress radio noise generated by the injectors. You can replace it with any similar braided strap of equal or larger size, available at most auto parts stores. It's not critical - just something that is similar.

It's almost certainly not your problem, but it's a good idea to replace it anyway.

Check the fender ground near the battery, too.

 

Make sure you get all the grounds that attach to the stud by the dipstick. There are a lot of grounds that converge there.

 

So after contimplating, decided to replace the main harness that runs around the bay and inside the dash.
already had a bunch out from changing the alternator and power steering pump. Also wire wheeled all the grounds.

So I ripped apart the bay and interior, got the harness out and put in a used one from eBay.

Connected everything back up. Put my ecu in with the relay and the jeep wouldn't start (figured it wouldn't since the ecu was bad too). Threw my friends ecu in along with the relay, no buzzing anymore before starting. Starts up easily, voltage is now at a normal 14 ish volts, and idles smooth.

Not sure what fixed it but everything seems to be good.

Just have to drive it around and pray nothing pops up/ the monitors clear out at least two.