Can you please run Windows Task Manager and see if a lot of CPU is being used by "devenv.exe", possibly most of one core? So if you have lots of cores it won't look like much as a percentage, but the core by core display will show one core maxed out, if that is what is happening.
Is all of this code in your solution, or is part of it in the stable include directories?
Do you see this when typing double quotes into a comment block, or only when typing into code?