Help me diagnose P Codes (Misfire)

Double checking error codes, I went from having numerous codes (I think I had all 6 misfire codes), to now just showing P0304 and P1399.

Honda COP coils are dog-E36 M3 after 80k miles. I'd replace them all.

Car only has about 70k miles.

In reply to Beer Baron:

Think of it as a normal distribution with ~80k as the nominal value. I can't tell you what the standard deviation is, but I would suggest that your coils are under suspicion IMO.

[EDIT] This thread from S2KI.com Suggests the nominal life is around 100k, but describes symptoms and DTCs similar to yours. YMMV. That thread also lists FLAPS replacement part numbers that are the same as the Honda service part i.e. Same brand, different box.

Rented a compression tester. Should have done this earlier:

Cyl1 - 220
Cyl2 - 215
Cyl3 - 210
Cyl4 - 110

Well... looks like we've found where the problem is. I'm rather irritated at the dealership who told me it was that I had non-OEM spark plugs. They had the spark plugs out and didn't bother to compression test for a misfire code. berkeleyers.

So... oil looks good. Not seeing any smoke or anything from the tailpipe. Problem is on a single cylinder. I'm thinking issue with exhaust valve.

Update: Head is off. Found an exhaust valve on Cyl4 that I can see a crescent of daylight around the rim of when I look through the exhaust port.

Now looking for a machine shop that will inspect the head and replace valve(s). Turns out one of the regulars at our bar who is a massive fan of my brewing work is an excellent Acura tech with over 20 years experience. I've been discussing the issue with him online. He's going to let me know tomorrow what machine shop they send things to when they need head/valve work like this.