Taking the valve covers off to set timing is not needed. You state that when you are at the 9 o'clock sprung position and turn it 90 degrees more to the 12 o'clock, it sprung and stayed there. The TSB implies that it could take up to 9 revolutions to find the right spot, so with our heads being 2 cams and 12 valves per head, I would continue to rotate it clockwise until it again springs to the 9 o'clock position, looking for the one time when it will not spring back to the 12 o'clock and you have to hold it there on the mark to install belt per the TSB