I can't remember exactly, but i was sure the speed recommendations were for climd and descent only. In cruise disconnect auto throttle and set thrust as per the fmc and fly whatever speed you get.
Where do you think they came up with those FMC numbers?
7. Thrust
Engine ignition should be on. Make an initial thrust setting
for the target air speed. CHANGE THRUST ONLY IN CASE OF
EXTREME AIR SPEED VARIATION. The FMC cruise page displays N1
target values for turbulence.
If you're climbing or descending, you pitch for speed. In "level" flight where the jet is being shaken, you need a target N1 to get the target speed. The speed is the goal, not the N1. And that goal doesn't change whether you're going up, down, or level.