FBO plate over advancing

Sounds like you're on the right track. I have said this hundreds of times. DO NOT TRUST A DIAL BACK TIMING LIGHT unless the advance mode is verified. Heck I have seen 0 off also. The potentiometers wear out and gives assuming results. Check it with a timing tape or against a digital light or it will drive you nuts. Also that advance cam will only give you 15 dist degrees maximum The FBO plate can only keep that or go lower something to keep in mind also.