If my tuner is set to 91 octane can I run 89 octane. It's set under strategy tune don't have custom tunes yet

 

I noticed that my 93 race tune left my cooling fan on constantly and for Chicago weather it doesn't work out well in the winter. Also I've been having long crank time/trouble starting my car after it sits all night when the race tune is on. As soon as i change it to the hyrbid tune or performance tune it stops. Also on 93 race when i push the clutch in when coming to a stop my car acts like it wants to die out. The rpms bounce down to 400 or so and keep going up and down till it smooths out after 10 seconds. Anyone have an idea what this is ? Only happens on the race tune.

 

No, don't ever run a lower octane than what it is set for, could be very bad for the motor.