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I updated my post (#27) with red text. Here are some additional details:
Spark plugs: BMW OE spark plugs (12 12 0 037 244) made by Bosch. These are the factory spark plugs for the 1M.
Ignition coils: Delphi (GN10571-12B1). This is the same part as the BMW OE ignition coils (12 13 8 616 153) made by Delphi and specified for the S55 (and also N55) engine. After doing some online research - and according to Eagle01's dealer (see posts #25 and #32 of this thread) - this seems like the best ignition coil for the N54 at the moment.
Note: The above parts are also exactly what Eagle01 used, but I think he purchased his ignition coils from BMW in the BMW box.
Before starting the project, I went for a drive so I could have a baseline to compare to after I finished. I got the car up to temp and tried replicating the misfire (again) by accelerating from 2,750 rpm in 4th gear. The engine began to misfire at 3,100 rpm and the check engine light came on. The check engine light went out after a short time, so I accelerated from 2,750 in 3rd gear. Same thing. I went home and ran the diagnostic using Carly for BMW and once again had the misfire for cylinder #3.
After letting the car cool down (important), I got started. The project took me two hours start to finish. I was definitely taking it slow because (a) first time, (b) it was cold(!), and (c) I took the opportunity to wipe the dust and grime off a few engine bay parts with a microfiber towel while I had the engine cover off.
I take my time when I'm working on cars (it's quiet and nobody bothers me, unlike when I'm inside our house, lol), but if I wanted to, I could probably do the job in 75 minutes or so.
Some observations. I think you'll definitely want a 9-10" socket extension. I had a 6" extension and it wasn't very helpful for cylinders #5 and #6. I was able to get #5 done with the 6" extension, but I actually went and bought a 10" extension because I needed the clearance for my torque wrench on cylinder #6. There's a strut tower brace that makes it a little difficult to get to cylinders #5 and #6 without a 9-10" socket extension.
This was the first time I've removed the engine cover. In the process removing / moving some things around to get to the engine cover, I noticed a couple of plastic clips had been broken previously (last time the spark plugs were changed at the dealer?). Frustrating, but what can you do? Everything is still 100% functional, but now that I know about it, I'll track down what I need and replace the parts. Moral of the story - be careful.
Overall it was an easy DIY job, pretty relaxing, and very gratifying.
And most importantly, no more misfiring and my 1M runs like a champ again!
nachob I hear you about doing the spark plugs first and then the coils to isolate the cause. That would definitely be ideal but I didn't feel like putting everything back together twice. I did stick with the OE spark plugs like you recommended so the only part number that changed was for the ignition coils. Everything seems perfect, so I think it's safe to say the Delphi coils are okay to use for the N54.
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