I have a 02 Chevy that shuts off the ignition when you turn on windshield wipers or resume cruise control button is pressed. This will happen at 20 to 75 mph. Sometimes when you activate the turn signal.
I have a very close combo and just made 600 with a failing cp3. loosing rail at 2200. I will be adding a 10mm stroker pump and also have manifolds, up-pipes, and bd intercooler, flex a lite fan kit on the way then back to danville to fine tune it.
I have hd S6020TD with no muffler on both my lb7 and lbz. The lb7 I took out a single stack was much less in cab than with stack. The lbz is very acceptable it is loud in the upper rpms but very manageable no complaints if you leave the muffler in the system I think you will be very happy.
Mine is the opposite tow haul is always on if I shift it back to R n D sometimes it will go off but most of the time it is on button does not work. I will pull the column cover to investigate.