Hi,
From your link the full uninstall command is:
C:\Windows\Microsoft.NET\Framework\v4.0.30319\InstallUtil.exe /u C:\Program Files (x86)\Intel\Intel(R) Extreme Tuning Utility\XtuService.exe
Maybe the service is white-listed by FRST because its from Intel!
If the Event Viewer continues to show "XTU3SERVICE failed to start" then the service exists and is trying to load use the sc command to delete it.