[Excaliber]

I got that model because I wanted to be able to disconnect the auxillary MSD box and wire the dist direct in case of a failure of the box. Generally it is not recommended by most engine builders because of fear the vacuum advance unit will advance timing TO far. From an engine builders perspective with warranty issues it's always a safe bet to err on the side of caution.

I've run mine with and without the vacuum advance hooked up. Currently I'm not using the vac advance, but it's yet another item I like to tinker with in search of the 'perfect setup'.