device.present lag iOS iPad1

Hey everyone, Just for some background, I am working on a 2-D game which uses a full screen quad to render the background of the game. I'm in process of adding some scrolling weather effects to the background, and ran into some problems while testing on the iPad 1.

Running the shader after making some very small changes ( usually an extra addition or multiplication instruction ), I find that graphics.presentandsync and more specifically, device.present wind up taking a very large portion of my render time ( 20 - 30 ms in the profiler ), where previously they were not taking very much time at all.

Adding extra objects to the scene (even transparent ones) will show an increase in rendering time in the profiler, but doesn't cause this insane jump in device.present.

does anyone know if there is a penalty for having a slightly more complex shader on a single object as opposed to several simple shaders on multiple objects?

to sum it up, are there any known bugs with device.present in unity, and what exactly would cause performance issues like this?