Have a 1993 5.0 with 14k miles car ran fine then one day it started take a long time to start it crank and can hear it pop like timing off then start die start die then start and stay running popped codes 21&24 drives ok kinda sluggish ran 96% of the gas out to make sure it wasn’t old gas swapped a known good ecm still the same problem any idea on where else to start