h4nh,
I feel bad for you but no offense that was a pretty damn stupid move on your part. If the owner and manufacturer STRESS running 93 and not only do you use 91, but 89??? WTF!
Sorry if I sound harsh but you probably shouldn't drive an FI M3 to begin with
Enlighten me on why you put 89 in the car? Stupidity fascinates me. I'm not ESS or Biglare who sold you the car so I can tell you exactly what everyone is thinking...