Have you checked for diagnostic codes? How to do so is covered in the MKIII FAQ section. As for Karman Vortex, that's the type of airflow meter used in the 7M-GTE (turbo models) whether you've got a GTE or a GE (which is all that was available until '87)... well, I'm not sure why you bring that up unless you've already diagnosed more than you've posted. A bad airflow meter (either type) could cause these symptoms, so could a bad knock sensor or several other things. Check the codes and post back with whatever you find.
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