Ping PIng ping Ping ... can happen if you advance it to far...especially how rpm high vacuum (mbar) tuning = correct timing and air fuel, a combination of both will revival greater benefits. But when you change / move the dizzy to advance your timing your putting advance everywhere, tuning puts it where its needed… ie Idle should be 16deg ;-) and low rpm high throttle should be negative / set ignition…… on a typical B engine.