I have had random misfire occurring for a month. I post this because I seen people post many times guessing and guessing. My fix which came from Subaru Techline (since the dealer service had no clue for 2 weeks) was a new wiring harness. The could have troubleshot the existing harness but Techline said to just replace it.

This is just one of many potential fixes. Glad it worked for me. I was driving a volvo loaner for a month ewe.