Inertial sensor turn help

I think you shouldn’t call abs() for gError statement, since you need to know the sign of the error. You want to have something like this:

while(true)
{
   double gError = angle - Inertial.rotation(deg);
   if( abs(gError) < 3)  // we will stop within 3 deg from target
   {
      break;
   }
   double speed = gError * Kp;
   leftBack.spin(fwd, -speed, velocityUnits::pct);
   ...
}

leftBack(stop);
...