Subaru Cold-Start MISFIRE? (Diag & "Repair")

At 200k miles, owner of this 2003 Subaru Outback says the engine "shakes" for about 10 seconds after a cold start with the CEL flashing....Then it runs smooth! Hmmm P0304 is set, so let s take a look at cylinder #4. Is this BAD NEWS for this Subaru, or can it keep going for another few years? TESLONG NTS500 DUAL CAMERA BORESCOPE: ***SAVE $50*** https://www.amazon.com/dp/B07SQ4FLYX?linkCode=ssc&tag=onamzpineholl-20&creativeASIN=B07SQ4FLYX&asc_item-id=amzn1.ideas.BH34H8T28VY4&ref_=aip_sf_list_spv_ofs_mixed_d_asin Enjoy! Ivan