so, if i understand correctly, the 3y is timed at 8 deg. btdc (not 12 like 4y)while plugging the vacuum lines. when reconnected, does it jump up like the 4y? to what exactly? after doing a bunch of work on the van i attempted to check timing, was a little off, but did not appear to advance when lines were unplugged. bad vacuum advance? how to test and fix? van seems to run great, tho! makes me worry.