rereading my own post, as ironically my throttle body now actually does have a fault. The "Command Throttle Actuator" value (which I think shows the value the engine wants) behaves as expected when foot comes off the pedal or engine is stopped, however the throttle position it self and relative throttle position remain always at 85. So it is stuck open. You can feel extra shudder when the engine stops, which I guess is a symptom those modders who remove it have to live with.
I guess I will get a new throttle body and fit that.
Whilst I am revisiting this post I can tell you what caused the odd vibrating at the engine speed this post was about - it was the crank shaft position sensor wiring. It actually ended up regularly killing the sensor it self. I bought a donor loom and spliced it from the ecu below the wipers all the way down to the sensor. No problems with that since.