Does truck have tuner installed now?
All tuner and tunes I know of only have exhaust brake on stock or tow tune. I have a del;6;3: 2016 with tyrant tunes and only get exhaust brake on Tow Tune.
Drivers side bundled up high under dash.
Need to be contortionist. Pass thru wires is under master cylinder and fuse panel under hood. Easier to take down drivers side inner fender well to access very short wires
2016 350 Lariat crew cab dually long bed Ruby red 2 tone ultimate lariat navigation sun roof 3.73 heated cooled front seats
5th wheel prep bought new in May 16 one of last of 16s built at least dually
Great truck traded in a 13 250 cc sb same color and options. I had added 20”wheels 35” tires...
Have you checked that your wheels are hub centric not just tightened down on lugs. Critical that proper centering of wheels with the weight and tow capacity of superduty trucks.
Don't have a 17 but have read that the upfitter pigtails are taped to harness under the hood on drivers side just below the the relay box. Should have rubber dipped ends on wires. Good luck!