After we've quit amd when we sleep, there are small hairlike appendages that line our bronchial tubes called cilia that sweep the crap out of our lungs. These are paralyzed when we are still smoking.
For a former smoker that includes the tar that built up in our lungs. It sometimes collects in the back of your throat and then gets on your tongue from the saliva. That's why you taste it.
Normally it goes through your digestive system and if you aren't careful will stick you to the crapper. If you find yourself clearing your throat it is because of this tar.
I cleared my throat past my first year of quitting.
PS: Dpn't get stuck on the seat! :-)