Suggested FSX autogen fix
Since autogen seems to impacting peformance, Matt Fax did some fiddling. See this post on AVSIM. It’s an experimental fix, so make sure you back up first as Matt suggests.
I gained 8 fps in the San Juans (default flight), and the same in an urban flight near CYVR (that’s 30% or more), just with the autogen fix. Thanks to Matt and to Bill Womack for the tip, and his thoughtful insights.