FPS Increase in VC w/ 2D Popup

I've been tweaking - as usual - FPS on my sytem and have a consistent 30fps using the settings Ryan posted for Nvidia Inspector on the 4Xs settings.

CPU = 4.0ghz 8-core

GPU = Nvidia GTX 660

VAS monitor has me w/ 1500mb free - so no issues there.

I have 30fps outside the aircraft.

In the VC if have a frustrating 9 to 15fps - over land, over water - doesn't matter.

When I open a 2d popup in the VC, such as one of the FMC's - FPS jumps up to 25.

I doesn't matter where I drag the 2D popup, I have a big FPS increase wiht the 2D window open.

Any logical explanation for that?

By the way, I have 8fps in the performance section for the VC displays.

Help/suggestions? Thanks.