Wa Alaikum Salam.
IMO, For 2008 EFI Cultus, normal petrol is fine. You may just prefer and go for Euro 5 fuel, but no need for high Octane.
Slight improvement in drive feel and fuel efficiency, however, it definitely comes at high cost compared to normal fuel, so no benefit, as cost-to-benefit ratio might be the same in both cases.
Then excessive carbon deposits on exhaust system(s), etc.