20 deg mech adv is on the high side, may want to try about 14-15 and bump the base up to 20 ish again. But if it is rattling at WOT then the changes to the mech limit may not matter. I see the vacuum adv is not hooked up so that is not the issue. Ensure he dist is really clean and the mech adv is free to move and wont hang up. Its got the heavy springs so the curve is not agressive
I am un wise to the ways of the qjet but it may be a lean AF ratio causing the ping issue. Check the fuel psi, filter and jetting + carb functions etc. If the motor is carboned up that can make it rattle as well.
vacuum leaks?, the basics