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I'm almost 100% certain it's the injector. With one of the boneyard injectors swapped into the #6 cylinder, it's idling on 5 cylinders and starts running on all 6 when it gets over 2500 rpm. I can hear it smooth out and the power gain is quite noticeable.

With the second boneyard injector installed in the same place, it doesn't fire at all, ever. Took it on a 30 mile drive, still missing.

The wires are nearly new Beru. I know new can also fail. It checks good for continuity and resistance and sparks evenly and strongly when disconnected.

The guys at M shop, my area's premier BMW service boutique, suggested I just run some injector cleaner for a few tanks. What do you think?

My car is a daily driver, so I would like to avoid removing the injectors for cleaning and balancing. Also, I need to drive to Las Vegas by Thursday night. Do I bite the $96 bullet and buy a new injector? I can get one locally tomorrow.

I called around to some shops for pricing on professional injector service (in-place). $89. Seems like my money would be better spent on the new injector to me.

Greg- I wish we'd had some time to chat, as well. I could've saved you a trip to the other 2 yards... I had just been to both of them and found only a sunroof deflector.

Have you checked the wiring connections to the questionable injector?

That was my initial diagnosis, shorted injector wire. It is delivering power, even while the wire is wiggled around, bent, etc., in an attempt to short it out.

I also swapped that plug with the plug for cylinder 5, which does not miss. The problem remained on cylinder 6. Cylinder 5 runs great even with cylinder 6's injector power supply and spark plug.

There is only a very minor valve tick, so I have ruled out the possibility of a loose eccentric valve adjuster. I'd hear that happening.

I am almost positive the problem lies with Injector 6. I am running Berryman B-12 Chemtool through the gas right now. I'll run a different injector cleaner with each of my next few tanks of gas and see if it clears up. If not, my local Bosch guy has the injectors in stock.

Update:

I made it to Las Vegas. I've still got a miss at idle. It goes away with accelleration, now disappearing at 2k rpm.

Well, that is, until I got stranded when I went to lunch. I'm thinking fuel pump. It started right up, but started stumbling and died before I pulled out onto the road. Fuel pump can be heard running with afm propped open, but the cold start valve hose doesn't feel firm to me.

Bang on the pump body with a screwdriver handle. If the brushes are worn out, which is how they fail, sometimes you can reseat them to buy a few more miles. Not enough to drive back to So Cal from Vegas, but maybe enough to drive around town to find another pump. Remember E28 pumps and early E30 pumps fit also. (and E23 and E24 but you're less likely to see them)

Luckily, I carry a spare pump salvaged from an e28 in my trunk. Problem is, the car started and ran fine after I had it towed to my friend's house.

The problem has not recurred. I hope it doesn't plague me when I'm in the open desert on the way home tomorrow!

Problem solved. It was a bad plug wire cap. It tested good for continuity and resistance off the car. It turns out that, while installed, the spark was jumping. Swapped in a new wire cap, and it hasn't misfired once. Cost $2.17. Thanks to Lenny D for suggesting it 15 posts ago. I thought I had it isolated. I wish i'd had a spare set of wires to check it with.