I was going to guess that.  Honest, I was :-).  But just one correction:  The high exhaust temperature with one ignition off isn't due to "incomplete fuel burn."  The burn is virtually complete whether running on one spark plug or two.  But the burn RATE is much different.  With two plugs there are two flame fronts and the burn completes sooner.  The slower burn rate on one plug means that a significant portion of the burn happens during the expansion stroke and less heat is converted to power.  Hence the exhaust temperature is higher.  Further, when the mixture is leaned past the best power (or maybe peak EGT) the flame travel is even slower and consequently the exhaust temperature will likely just continue to go up when leaning, not peak and go down.

Most people have had great luck with the Lightspeed system, but I am on my fourth in just 400 hours with none of the failures were due to installation errors and all were different problems.  The last one has been running perfectly for over 100 hours, so I guess I'm past the near side of the bathtub curve :-).  Klaus was never very forthcoming about the failures, but here is what happened:

1.  With about 10 hours on the plane the inverter power device for one channel (two spark plugs) quit and then after about 10 minutes it completely shorted and blew the fuse.

2.  One of the channels started to intermittently trigger off the previous channel, putting the spark at about 140 BTC.  Now, THAT gets your attention.  Fortunately, it happened on the ground at the beginning of the takeoff roll.  No real explanation, but "later model" components were installed.

3.  One of the channels would quit after 10 or 20 minutes of flight.  Again, no real explanation was given.  The ignition coils were also replaced at that time as the "new" coils were supposedly "better."

4.  Still going strong at 400 hours.  I will say it starts and run faultlessly, and I REALLY like the improved performance above 10,000 feet produced by the extra timing advance.

Gary Casey