It was actually Originally posted by GTS_Rosh, but thanks anyway
I think I remember reading somewhere that when the butterfly valve is
closed it draws warmer air from inside the engine bay via channels in
the engine plastics that are right in front of the stock air box opening,
This is done to help the engine start and idle properly in cold weather.
Sounds like the benefits of removing the butterfly valve are few, but the
benefits of leaving it in are many.