Smoking Passionflower with DMT does not make the experience very much more "Intense" IMO. Passionflower is a weak MAOI and as a result, it does not affect the trip a great deal. However I have found it does increase the length of my trips a little.
As for the Passionflower syrup, I think you should try it, it sounds interesting. The levels of Harmalas present in the syrup could be high or low, so start with a low dose, or try some of the syrup on its own to gauge the strength.