When you lose power at 110 mph I believe that it is going into limp mode and it forces you to slow down to 60-70 mph because that is the max speed that having (it feels like) 30 hp will allow. When you shut it off it resets it until you trip limp mode again.
Look through the FAQ articles for the tips on adjusting or replacing the VNT actuator. There are some instructions on troubleshooting the system. I don't know where your N75 valve is but if you follow the vacuum line from the VNT actuator it will lead to it. If you felt the actuator move freely by hand the more likely cause is a vacuum leak or broken vacuum line. Invest in a hand vacuum pump to test the vacuum line and actuator at the same time. n75 valves do go bad but I think it's probably less likely than the other causes.
Look through the FAQ articles for the tips on adjusting or replacing the VNT actuator. There are some instructions on troubleshooting the system. I don't know where your N75 valve is but if you follow the vacuum line from the VNT actuator it will lead to it. If you felt the actuator move freely by hand the more likely cause is a vacuum leak or broken vacuum line. Invest in a hand vacuum pump to test the vacuum line and actuator at the same time. n75 valves do go bad but I think it's probably less likely than the other causes.