That it's not lean like some ex'spurts claim.
If it was lean... it would surge at cruise, not necessarily ping at all. I swear ...some people read a bunch of **** and think they mastered the universe. Lean tune... if it's that lean, you're already breaking ****.
34 or whatever is too much total timing/power timing for the octane and your dynamic.
Bring it down to 25... then drive it and increase it 2 degrees at a time till it pings again....then take 2 out. That's what your motor likes on the gas you use.
Remember what I said to you in my first response, 25 is all I can run and I have a hair more than you ...so if you're pinging at 28, lower it to 25... if you're still pinging go to 23.
It's not that your carb may not need tuning, it's just well known you cant run that much with that amount of cyl psi.