[buzzinhalfdozen]

From my personal experience, the digital type advance timing lights are the ones I've seen problems with. I have a decades old MAC, dial type advance light I've used with no issues on MSD ignition systems. Still have an old non advance light that I'll occasionally throw on just to verify. Friend of mine had a Snap-on digital advance timing light he used and was having some issues with his engine not running correctly, he asked me one day to borrow my timing light, his timing was off over 20 degrees. He set his timing and took that light out of his trailer.