Ah wow, 30Hz, okay. Rare case, but understandable.
Pet peeve alert: Don't ever compare one product to another. They are not even remotely close to equal and I hate when people try to do this.
Unfortunately, I don't. The explanation in the CPU thread about all this explains the situation on a high level, and on a low level as I understand it, I can make sense of why it's happening, but there's nothing I/we can do. At the end of the day this comes down to texture paging and how it's done in X-Plane. The most common folks effected are those like you with an Nvidia 1xxx series video card. With exception there's others, but by far and wide that series of video card struggles the most with this issue in our gathering of reports. If you haven't done so already, you can try and give yourself a little more headroom with the 6GB optimized version, but that's really all I have.