Me being a bad one for "showing my dumb side", I am still thinking this could be a false timing read. As I read the literature, these MSD can double or triple strike each spark event.
I had a bad experience with that method, while working with a fellow who wrote the double-strike spark code used in some early OBD II Ford software. When our supercharged engines (with add-on spark processor he wrote code for) had high cylinder pressure, and a lean mixture, the "first spark" didnt make the jump. The second one did, which was late in time-event, and then caused our fast 32-bit engine ECU to detect the change in crankshaft revolution as a misfire event.
This shouldnt be an issue with a race engine, of course, unless that spark plug is surrounded by highly compressed air with the gasoline not yet vaporized enough to lower the electrical resistance of the compressed air. If that happened on a multistrike system, your timing light will only flash on the following spark and the engine wont rev cleanly.
This late vaporization can be really ugly. I have had this "heavy fuel" discussion with a number of folks experiencing lack-of-rpm, misfire, low-power, black sooty-exhaust, high EGT, and burn in the cylinder so bad that they smoked pistons. These are very experienced people that are really good, but got bit by this issue as I did.
I will butt out now, but this sure seems similar to what happened to us, (and some really top notch teams). Sometimes the old "its the gas" story can be true. When the only thing youve changed is the gas...well, thats how my 76 year old Mom figured it out for me at Speedweek '98. After two days of frustrating inspection and attempted repair, she was the only one with the right answer in our pit!
If it ran fine, and you didnt change anything.....
....and if you already tried some fresh, lighter gasoline, my apology for wasting everyones time.
JimL