Ohh!... I think that baby is chromed.... not good for filing...  she'll rust up...

I think you're still mostly on the pilot at that throttle... is it possible, that you are interpreting small wind gusts or changes in air density, as surges or hesitations?...
I ask, because I've done it myself....  Here in the desert, you can feel little pockets of hotter and cooler air, that must be the size of a small wading pond... come and go in a fraction of a second...