Are you sure it's the pitch axis thats causing auto pilot to "kick off"? I would check the rudder axis on the X52 as it uses a potentionmeter and is prone to spiking.
The pitch and roll axis use halon devices and rarely mess up,there is a magnet mod that you can do that might help in this case,check X52 mods on Utube!
Also you could enable scaling and move all the sliders to the top of their range and see if that doesnt make the stick more responsive.
Hope that helps.

Just FYI. Disabling scaling is the same as enabling scaling and keeping the sliders all across the top.
To see which axis is spiking, simply watch the numbers in parentheses, next to the axis, in the "Map Controllers" panel. If the numbers are changing, with no input from you, then that is your problematic axis.
What you may want to do is to add some deadband to that axis. Select the axis, open the "Advanced" panel, then look at the input graphs. The goal is to add enough deadband to prevent the spikes from getting through the game control (the graph on the right will show the results of adding deadband).
Hope that helps.