Whether or not you need to shift down a gear depends on the approach speed before a turn or hairpin. If you brake really hard, chances are you need to drop down a gear to come out of the turn faster.
If just releasing the peddles, then you probably need not shift down and stay in fourth. I assume you are using the integra.
To cut across (the 'shortcut') the brown patch, usually you will be in 3rd gear doing anywhere from 80+ kph to 90+ kph.
Hope this helps.
