The weed residue itself probably won't do all that much potency-wise... with salvia, the goal is to get alot into you, and quickly... but by the time the weed kicked in you'd probably be nearing the end of the salvia experience. As for flavor though, I've definitely noticed my bong tastes different for a while after I smoke salvia out of it (i've learned to just use a different slide for that stuff now)... so if you're really liking your herbal flavors, you might want to consider getting a cheap ass pipe for the salvia. As for the last part, I've smoked salvia extracts out of pipes many times to great effect, but never really had a great experience with the dried leaves that way.


Then again, this is just one man's opinion.