P0305 code keeps coming back, what to try next?

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Hi, all, I would like to get some advise please? I have Mazda MPV 2003. Recently I got P0305, cylinder 5 misfire. When I had this, I did in deed feel misfire, engine RPM dropped from time to time, and felt it would stall, though it never did. Anyhow, I hear P0305 is a common problem in MPV. I replaced spark plugs/coils for cylinders 4,5 and 6. Misfire appears to be much reduced (pretty consistent idle, though minor shake while accelerating), but P0305 keeps coming back (I reset the code 3+ times). I don't get any other cylinder codes, just P0305. What else should I try next? Is it ok to keep driving while engine light is on? I did look at this page: www.obd-codes.com/p0305 This page talks about checking Oxgen sensors, etc., but if these are bad, I assume I would get additional engine code in addition to P0305. Any info is appreciated. Thank you!