How to stop the pinging

[Cox76y]

Getting sick of chasing my tail with this bike. I'm currently running the jd red needle, 3rd clip with 172 main and 42 pilot. I only just moved needle from 2nd clip to 3rd position as I'm trying to stop the pinging on deceleration. It's terrible. I haven't ridden it on the 3rd clip yet but running the bike in the yard it's still pinging. It's a19 gasgas 300 with the head cut. Not sure what the squish is at but it was done by a reputable business who have done my other bikes. I'm running at between sea level and 500 meters. Any helpful advice would be appreciated. Thanks