If I run my impreza on Maxol E5 (98/99ron?) will it be safe? it's not mapped so just thinking if it was ran on that without booster it should be ok?

I dont rag the car or drive it on, its had 40 quid on 95ron as i needed to put something in it to get back but has barely been driven over 3k rpm.

If I do a track day I'd put in E5 and a bit of octane booster to a full tank which would equilevent jap fuel?