Yes, if the tuner stored your stock tune, you can put that back in, then re-install the 91 race tune.
To be completely sure, contact the support tech group of your tuner. tell them exactly what happened, and let them tell you for sure; they should remain on the line while you perform the action. You don't want to get your PCM/ECM locked up over this.
Ask the experts. Talk with the tuner tech support group.
It is better to keep your mouth closed and let people think you are a fool than to open it and remove all doubt.