Once your car hits Spec 5, you will notice a dramatic increase in speed.
For most players, this will result in either understeering and hitting the outside wall on many turns, or being forced to attack corners with impractically slow entry speeds.
The way around this is to drift the turn. The out-in-out principle of racing still applies here, so keep that in mind.
Essentially, your goal is always going to be to clear every turn with the highest possible exit speed.
Utilizing the BC and causing your tires to lose grip (while finding the right angle to clear the turn on a good line) is a must-have skill in ID 7.
View the basic footwork here:
The timings of when to shift, when to turn the wheel, etc will vary widely depending on the nature of the turn itself (your angle, your entry speed, the structure of the following turn, so forth and so on), so there are a million different variations of attack. This is part of what makes the ID series so much fun: the extremely steep learning curve.