I'm not sure about this switch under the selector, but I do believe there is a microswitch in the throttle pedal itself (inside the car) which can give a false reading and put the throttles into limp-home. It could also be a problem with the EA control module itself. Theres a few other things that could throw this into limp-home, if I were working on it i would hook up the HHT and monitor the actual values of the CTP switch. I wouldn't bother with the 20 mile roadtests (as much as I love hearing the M120 purr), instead I would do what you did, drive around the lot 20 or so feet at a time, then stop, 20 more feet, etc. Yes, "both throttle motors" didn't sound right to me either.