What is the Sixth Step of MacBook Repair?
Take it to Apple and ask them to fix it under warranty.  If you have made a clean install, and can still demonstrate the problem, you almost certainly have some sort of hardware issue.

If you did a reinstall, then added something that has a kext, that might be responsible, though, so in the (unlikely) event, reinstall, don't install that, and see if that fixes the problem.