190Evan

So I recently picked up a 400e a few weeks ago and was given a few issues. This week I am replacing the transmission and a few other little things. BUT I have a question for the members on here. Im stumped. There is a noise coming from the front left side engine bay that sounds like a lawnmower/exhaust leak/air leak. What first came to mind was the secondary air pump but I just don't know enough about them to diagnose it. Im curious is anyone on here could help me out. The noise will stay there until I rev it past at least 3500 after that it will silence and go away. But That why I believe there is a leak somewhere, Could it possibly get clogged or closed up by something after revved? I have no clue, Please help.
Also Im hoping this thing has a bad engine harness because its throwing 17 different engine codes, some related to the transmission but I would like to believe that they are all related to the wiring harness. I inspected it briefly and saw a few exposed ground wires, but then again I don't know enough about these chassis yet to diagnose it instantly.Thanks for the help