Wanted to share with all that I added a surge protector to my 350M, as I am weary of campground power boxes. Anyways I added this particular one to my unit
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http://www.progressiveindustries.net/ems_hw50c.htm
I had it on my old TT, but took it out before I sold it. I read the F.A.Q on progressive website and they said to install this before he transfer switch. Well at first I couldn't figure out where that was. But the other day I went to use my InterVac system for the first time and when I plugged the hose into the socket, the unit didn't turn on. So I tried to pull the vacuum off the wall in the storage compartment to see if it was wired up, that's when I saw the transfer switch. So, I pulled the false walls out in the storage compartment, disconnected the AWG6 wire coming from shore side and installed the surge protector before the transfer switch.
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I then ran the remote display wire from the unit, through the wall were all the wires go to the main breaker panel in the pantry area and then passed the wire up the wall to the top by the switch panel. I then secured the display by the command right double side tape (I don't like to put holes in my walls). So now, when I plug into shore power, there is a slight delay before the power kicks on, but when it does I can see if there are any errors in he wiring and see how much voltage is coming in on each leg.

I highly recommend this device to protect your investment.

PS. I did get the InterVac to work, they had to send me out a new piece to put on the hose that had a metal ring around it. The other one was all plastic. The metal ring contact two metal prongs in the connection, which completes a circuit and turns the vac on.