Here are my settings to speed Visual Studio and in particular IntelliSense up for C++ development.
They should make working with C++ in large codebases more responsive and faster (I’m using them with the Unreal Engine 4 source build).

Note: Automatic Precompiled Header Cache Quota is the amount of space you let VS use up in your .vs folder in Megabytes, so 5120 is 5 GB.
Set it based on the amount of space you have available.

Next, remove or disable any extensions not on this list (Extensions -> Manage Extensions):

Finally, run the Visual Studio Installer by searching for it in the Start Menu, click Modify, then Individual Components and uninstall IntelliCode:

If that’s not enough you can go deeper and start logging & debugging IntelliSense.
Read this for the details:

Let me know if you have suggestions in the comments below!

Mincho Paskalev
Have you considered vs-chromium?