The dreaded “exhaust mode selection not available” message being seen on some 2020 GT500 isn’t new to Mustangs as it’s also been experienced by GT350 owners. There are a number of reasons why the message can come up — from melted harnesses, blown fuses, sticking butterfly valves, failed actuators, to other reasons. M6G member Epiphany has spent a lot of time getting to know this exhaust system and shares what he’s seen to date.