[TomMiami70]

Thanks for all the replies and helpful tips. Unfortunately, the search for the leak continues. I may bring in a professional as I seem to be wasting a lot of money and energy replacing parts that don't need to be replaced.

Hi - I also have a 2008 43' Sovran, and I have the same issue.  We have replaced all the valves and seals and still have a loss of vacuum pressure from the forward head.  We pressure tested the hose that runs from the head back to the vacuum pump and it does not hold the pressure.  Thus we know this is where we have the issue.

Were you able to solve the issue without tearing apart the whole boat?  Was the line attached anywhere? 
Please let me know.
Thanks.
Tom