jetting advice again

[Cox76y]

Hoping one of the jetting gurus on the forum can suggest a fix for me.. Currently I am running the stock n7 slide,Necj#2 mj172 pj40 air screw about 1 n half turns. The problem i am having is coming down off the throttle to the idle\pilot jet I have a bit of engine noise that sounds very similar if not the same as pipe banging. I know that generally pipe banging is associated with running rich but I have already gone down 1 size on the main.
Is anyone running a 170 main on there 2018 300 or is there a chance its actually running lean on the pilot and making a sound very similar to that pipe banging noise?? Plug looks ok, there is spooge coming out the exhaust but this could be from running the bigger main jet previously.
thanks
Josh