I hit 5600 static rpm's. In the past, the best I could hope for was 5200, most of the time settling for 5100 rpm's.  I taxiied back in and installed the top cowling....max rpm's 5100.  Took
the top cowling back off....max rpm's 5600.  One more try....5100 with
the cowling back on.  It is beginning to become more clear to me, that
one of two things are affecting rpm's.  Option one is that with the top cowling on the engine is ingesting heated air and just cannot develop the same power as when it ingests outside unheated air.  Option two is the muffler bearing may be worn.  I'm kinda leaning toward option one.

     to all who reply.  Paul Conner