You are close in 96 they started using the torque limiter instead of a solid gear and this has protected the starter & drive gears from that nasty back spin at shutdown & during a huge backfire. It's possible the cam changed but I just don't buy it , I'm sticking with stock carb & exhaust and more
The carb it to blame. I have the webcam standard grind a little more lift & duration as well as the vm36 & header which may account to not having any backfiring. And that false spark and sharp edges in combustion chamber have always bothered me. I'm glad I unknowing bought a 96 for the torque limiter. As for the rest of it every motor you build you learn some thing new therefore you next motor reaps the benefits of all the previous engines and this engine has 15 to 20 engines ahead of it. I'm never in a hurry to build one , it's always better to take your time and make it right , attention to all the little details is a must and incorporating all you have learned.
Steak Tonight ?