Misfire at cruise, popping/afterfire at 3000RPM

Getting back to timing -- I don't know if you've seen the posts where we talk about how the distributor only gives about 10 degrees advance by 2800, so with 14 initial, I end up all in at 24 @ 2800 RPM.
I either missed or forgot that.
Remind me why is it all in at 2800?