93 Impreza idling issue

Hi all,
I have a 1993 Subaru Impreza with about 225,000 miles on it. It is a very solid car, but in addition to the throwout bearing starting to go, I am having a strange and hopefully negligent issue. Sometimes when I am stopped with the clutch in and the shifter in gear, my engine begins running very rough. When I pull the shifter out of gear and keep the clutch in, the engine begins to run normally again. Is this at all related to my worn out throwout bearing or something else?
Thank you,
Katy