Plenum is highly recommended, but even if you do not go that way, have a close look for leaks, particularly under the crankshaft.  The Lancair baffle kit has a huge hole down there, out of sight, out of mind.  But there are leaks all over including around the oil cooler.  Slits here, poor fits there and everywhere.  Cut bits of silicone baffle material with scissors, glue in place with silicone rubber.  I think I spent three days doing that.  When you inspect with a light, you  will find them everywhere.

 

Fred Moreno