Don't go for tuning, just fill the High octane and then check the result, the ratio should be 65-35 % of normal and hi octane, in these days the fuel quality is also goes down with the prices, in my office my several colleges facing the same problem (most of them have JDM version of auto transmission vehicles), even now the Honda 3S dealers recommend my one of friend to use the hi octane instead of normal petrol.