UPDATE UPDATE!!

I think I may have traced down the issue.

I noticed while flying along with steadily dropping fps, that when I hit Q to mute the sim, my fps jumped back up to 30 (fixed).

Tried this multiple times with similar results leading me to think that there is something about the sound files for the 727 and 757 that my computer does not like.

In a test flight with the 727 sound replaced with the 707 files I had absolutely no drop in fps.  I am assuming the same goes for 757 as well.

Im going to have to investigate my sound card and drivers, etc, but for now I am thrilled to have discovered the problem and being able to fly uninterrupted by using some modified sound files.

Hope this helps someone else. ;D