2001 ES 300 Engine ping when accelerating

[Cryoshotz]

So i have a 2001 ES 300 that sounds like its pinging inside the engine only when accelerating. It doesn't happen at a stop nor does it happen when just letting it cruise. I know some people have mentioned that it could be not using a high enough octane fuel but ive only ever used premium gas so i know that that's not the issue. First I changed out the mass air flow sensor, but that didn't fix it. then I also  changed the spark plugs cause a couple other forums have mentioned that it could be pre detonation but changing the spark plugs to NGK Iridium IX plugs didn't fix the issue. So my next steps are to change out the ignition coils and after that maybe the timing done??? but I have no idea what else it could be. has anyone else have this issue? ive seen a good amount of forums on the subject but most of them are inconclusive. any help or past experience on solving the issue would be appreciated.