Carl - Perhaps I can answer . The throttle plate you are looking at hardly ever goes past 1/4 opening when engine is running , even at full throttle . The Governor does that for you ,and is purely mechanical ; It in no way has anything to do with the ignition , although with the electronic fuel injection ,the TPS (throttle position sensor , MAP (manifold absolute pressure), Fuel injection module (computer) , can throw a fly in the ointment that most don't have to deal with . I have a 445 and been all through the workings of it . Sounds like you have an ignition High Tension coil , or the ignition pulser coil going bad , or just a bad connection to either (or) . The gov.will not be tied to your woes . Start thinking electrical/electronics , or possably fuel delivery issues , and pray that your fuel injection main module isn't the culprit . They are very very expensive compared to the ign. coils or pulser coil . I may be wrong , but I think there is only one pulser coil for the 445 , compared to two for the 425 .
Also the governor kicking in is probably a direct result of the ignition failing , or fuel delivery and engine speed faltering , not vise-versa .
Edit: Also - if it doesn't do anything weird while mowing - what are you talking about ?? That is when you are using the most power isn't it . Now I'm confused .
These connection issues , and file locking errors , are giving me fits!!
Dave