Been happy with P3D since I got it a few months ago. Lately I have had the FPS counter turned off, and have been flying the Airbus 320 I had been locking the FPS to 30 and when I was flying the majestic Q400 it stayed right around 30 fps. The last two days I noticed that the FPS seemed to be slowing down at larger airports like Denver, and Salt Lake City, in the Airbus. Tonight I took off from KDCA with the weather bad, and I saw the FPS dip down below turn as I was climbing out. I thought for a second that maybe GSX, which I downloaded and installed the other day may have caused it, so I uninstalled that, but no difference. I then ended the flight and loaded up the Q400, and back to 30 FPS. Is the Airbus that much heavier on FPS than the Q400, or do you think I have something else going on?  

The Airbus isn't THAT heavy on the framerate, but the Q400 is definitely better by about 3 to 7 fps.

Looks like a found the problem. I had installed GSX right before the FPS took a dive. I read on their forum that it should have no effect on FPS, but since it was OK before, I decided to uninstall it an see what happens. After that the frame rates seemed to be back to normal.  I then reinstalled it this morning, and now everything is as it was prior to the problem.