My observations: I've made some maintenance work on the engine, including TB cleaning. After that I usually get somewhat higher idle around 750 RPM and hidden 0507code (idle speed). Driving in this condition, the engine runs surprisingly clean, no pinging at all. After the idle relearning procedure, the pinging immediately came back. I regret I did it
can't get back to higher RPM, fooling ECU somehow. I prefer pay more due to the lower MPG (if it occurs) than destroy the engine by pinging