It really depends on the type of aromatic. For example, i sometimes smoke devil's holiday which is a strongly flavored aromatic, it does, to a certain extent ghost a pipe. However, the flavor is so pleasant that i don't mind. After a bowl or two of something else, it goes away. On the other hand, i could not believe how much ghost was stuck in a pipe from rattray exotic passion, C&D dreams of celephais and the one and only bowl i ever smoked of capt black grape. For the most part, i don't usually deal with residual ghosting as i clean my pipes on the morning following. I run cold water through the stem and use several pipe cleaners to swab out the stem, mortise and bowl followed by a paper towel "reaming" of the bowl. I then frequently use a bit of whiskey, rum or brandy in the bowl allowing it to run out of the stem. This is followed by vigorous use of pipe cleaners through the stem and into the bowl. While i have read that acrylic and alcohol do not mix, i have never had a problem with any acrylic stem. The one part of this i really recommend is running cold water through the stem as well as rinsing it under the faucet.
I just realized my pipe-cleaning routine is woefully inadequate.