Marc:
your right...and the effects are different...u can achive better cruising mileage when cruising and smoother idle than the other way....supposedly you get a quicker off the line start with vacuum manifold but top end performance isnt as good...but only really matters if racing...the timing does need to be changed when switching to manifold vacuum....i actally prefer manifold vacuum to carb...but thats cause my carbs vacuum is nothing so its useless and makes no diff when the hose is on or off....if your engine changes RPMs by about 60 RPMs when the hose is disconnected then your vac advance is working and doesnt matter...i think it would be fine running the hydrogen from the manifold...just not as completely evenly distributed...
