FCKNelite

Any resolutions to the vibrations? I bought a 2015 2500hd with 6.0, 76,000 miles and it has a loping vibration all the time. Park, neutral, drive, but the vibration is worst right at 53 mph. Had tires rotated and balanced twice. Drive line inspected, shafts, u joints, diffs, transfer case. They looked at everything they could see without too much disassembly. No codes/lights lights. Diagnostics show nothing wrong. Only thing I could find is the steering lines from the pump have a strong vibration in them, one exhaust bolt broken at back of manifold and the brake pedal gets a little harder if hauling a load but not so much that I’m really sure somethings wrong. Also turning from a stop seems like the wheel gets a little tight. Being new to this type of system I’m not sure if the vibration or tighter wheel in slow turns is normal? Been chasing my tail and mechanics are lost. Any ideas?