I will give you my experience and bad mouth Autopilot Central in Tulsa justly so.
I took my Ovation with KFC225 for them for a slight porposing, nose would go up and down slowly, airspeed would build up and then would go opposite direction.
APC tested the pitot static, tested the AI, tested the computer and finally decided it was a gizmo (forgot the name of part in the pitch servo), they replaced it and the problem still existed. I said stop and told them you guys clearly don't know what you are doing after spending $4000 or so. I was just going to live with it, till I was flying along one day on AP and the aircraft deviated nose up aggressively, hit the big red button and got plane under control. Continued my flight hand flying the plane, almost declared an emergency or two (sarcasm font). Finished my trip and started looking around for another avionics shop. Found a guy nearby who diagnosed the failure, the gizmo had a cold solder joint, so Autopilots Central can't even solder correctly. He then continued the diagnosis and determined that the motor in the pitch servo took too much voltage to start moving, I guess the computer sends voltage and waits to see what happens, it continues to crank up the voltage and then all of a sudden it starts to work and it just takes time for the system to equalize. Motor should start moving with 1 volt and was taking almost 2.5 to 4 to start moving. Replaced the pitch servo and it has been working perfectly.
Don't know if this is going to be helpful or not.
Good luck.