Still have an occasional reset/sync loss issue. After some poking around, I think this may be due to a voltage drop issue; most likely for the 12v switched feed into the Megasquirt ECU. I spent quite a bit of time probing around with my multimeter today. Reset usually only happens at idle when an electrical "spike" occurs - such as locking the doors, the A/C compressor cycling, etc. It doesn't always happen with those events. Sometimes it will happen without any of those events happening.
I have attached a VERY crudely done drawing showing what the voltages were at the various places I probed today. I think I may have either a bad capacitor or bad solder joint on the 12v switched line. These measurements were taken with the key on run, but the car not started, so that is why the readings are in the 11s. Please let me know what you think.