[Mike Brasfield]

If the knob is on the engine side of the footbox it is the clutch adjustment dial. sounds like your clutch is running out of material. Just like brakes, if you have to add break fluid your break pads are getting smaller. If you clutch is acting different it may be due to loosing cutch material. Turn the dial and try the pedal then try again. On the original mustang clutch you would lift the clutch pedal up with your toe to adjust. good luck