Finally got my HEI spark tester. Spark looks good and regular. I've already tested the plug which is good. As I said before the fuel injector is ticking indicating it is working. I assume the only thing left is a dirty clogged fuel injector. Anything else I might have missed? I planned on taking the fuel rail off and replacing the fuel injector. Is that the best way to go about it or should I just put fuel injector cleaner in the tank and go run it hard on the highway.

It’s worth a try with some petrol system / injector cleaner and some premium fuel.
Failing that I guess you are only left with mechanical failure of valve train or cylinder but I wouldn’t have thought so.
I probably wouldn’t wring it’s neck but try a little more spirited driving probably wouldn’t hurt

Update: I finished the #8 fuel injector replacement with a reconditioned one from eBay for $20. If the weather was better I would have done the valley pan while half way there. It took a while for the fuel to fill the rail. Then of course the battery was too weak so it needed a jump. Once it fired up and came out of high idle it was still running rough and the flashing service light was there. Same #8 misfire. I was not pleased. I need to charge the battery so I kept running it. As I'm keeping the idle up I realize I didn't reset the steering angle so I did the lock to lock with the wheel. Stilling running rough but no service engine light and iidtool not showing that fault. I clear all the faults. As I let it idle I notice the flickering of interior lights and display lights have stopped flickering. Seems to running normal again. Maybe it just took a bit to get all the air out of the fuel rail. Time will tell.

See how it goes, it is probably not over happy at having a low battery, like you say give a drive around to see if things improve.
Mine is still holding back and engine braking seems excessive so i am looking at CATS, checking coil resistance, fuel filter, even going to rebuild my calipers but my cylinder misfire codes have not returned.
I would take yours for a bit of a drive and see how it goes.

Any update with yours? I have been looking at my CATs and something a bit odd as the temp going in on one side was 175 Deg C and about 75 deg C coming out or around those figures and it has had two bottles of cataclean and a damn good thrashing and it’s been a lot better with temps on the cats much higher on both sides and it’s been pulling great again but I still think my cats are not right .

I have about 75 miles on it since the injector swap, vacuum line replacement and air intake to throttle body gasket fix. Runs great and no service engine lights. ....knock on wood. I have run a bottle of techron on an 1/8th tank and another is in the full tank.

Great news however strange! Current stable:
2006 BMW M6
2007 4.2 V8 S/C FF
Gone:
2002 4.4 V8 FF

Good news then

What seems strange Dan?