I imported a model 3ds to prefab3d. Added eight points of light. The performance was fabulous.

Exported to an as3 class, includes the lights and my app performance was a mess. Why?

Prefab runs on latest “release” branch (when I compiled it a few days ago for this update ). Tho I haven’t noticed a performance change as you describe.
Perhaps you could try to swap engine if you run on beta (“master” branch)

Prefab is using AIR 3.3. using similar runtime as player 11.3. Is your player a debugplayer? Have you tried an other browser or was it SA player? Is it 11.3?

The AS3 outputs on themselves are faster to init than same data loaded using loaders, but this is only during init. Once they have inited, the data that they have defined is considered by the engine exactly the same way as any other data.

If all the above is not changing anything/relevant, would it be possible that you may have added some code that is slowing down? or is loaded into a project using overlays in displaylist, components, other frameworks, are you using exact same textures(sizes) etc ?
Have you tried just adding the as3 ouputs to the view with no lights?

I cannot help you much more atm as I would need to know bits more about your project/setup than “perf was a mess”. There is no obvious reason I can think of that can explain this performance drop.