samosali:

The combined flexplate/trigger wheel of the M119 engine is a one-piece welded and riveted assembly. It is located on the crankshaft flange with a dowel, ensuring that it can be attached in only one position. The trigger wheel is of 63 teeth minus two (and does not have a flying magnet). The "minus two" window defines the crankshaft location for ignition timing, and the total tooth count is used to signal engine speed. The sync sensor(s) identify specific cylinders for both ignition and injection events.

You have mentioned a variation in ignition timing of 30 degrees. Is that a cylinder-to-cylinder variation? Or a random variation of up to 30 deg. at idle as observed at #1 cylinder? Has the same timing light been tested on other engines? Is it steady in other situations, or does it exhibit scatter when used on other engines?