You can if you change it to Map 0. Map 0 is the stock Map and the car will act exactly like normal on 87 octane.
That being said that means that you get zero benefit from having the JB1 at all and it would be better to keep it stock. You need to have at least 91 octane to run the JB1 on Map 1 which is the lowest setting. Basically if you are concerned about power at all, you should be running at least 91 octane, even on the stock tuning.
Thanks bro, I figured as much. Wanna hook up my kid with more power, but at the same time, she will end up having to up her Octane grade with her car a.ka. more expensive (which worries me she forgets one day at the pump) and car starts acting up.