The limp mode in an AGU restricts boost and in-directly acceleration but does not directly limit total speed. If the car can get to 107 before limp mode kicks in it won't accelerate further due to limited boost. If the car is going faster than this limited boost can maintain it will begin to decelerate.
As far as I know the limp mode on all AGU's is temporary and can be reset by lifting your foot off the accelerator and re-applying. But if the conditions that caused the initial limp mode are still occurring it will go straight back into limp mode.
Like the others said, check for boost/vacuum leaks, stretched throttle cable (this can be adjusted using the holder that attaches to the inlet manifold)
I suffered from limp mode when my cat disintegrated and started to block my exhaust system. If you can, take it off and give it a shake and listen out for any rattles.
