I would wholeheartedly agree with everything above, esp. the part about not condemning the throttle actuator. Everything I've read talks about going into limp-home mode while cruising accompanied by ASR light coming on.
There is another thread today discussing 400E wiring harnesses, and one of the posters does comment that limp-home mode can be triggered by a bad harness. I'm due to have mine done; has a number of areas with missing insulation. Check your harness first. An easy place to look at is the wires going to the individual fuel injectors, esp. the brown ground wires as they are not covered by a sheath, only their individual insulation.