Usher,
Doesn't sound like "limp mode"; a protection that limited RPM to I think around 6K.
Does it cut out at 8.5 exactly, every time? Does the red light blink? Where you in inclement weather with traction control on?
Only unexplainable engine cut off I had was when I pinched the main fuel line under the fuel tank. However, it was based more on throttle percentage than RPM - if I asked for too much fuel, it would choke. If you removed the fuel tank or fuel pump recently, check that line isn't kinked.
Good luck.