help annoying pop in exhaust

I have a rebuilt .040 360 stock rotating assembly 1.88 j heads milled .015 valve job new seats comp springs lifters timing chain comp thump .486 edelbrock intake holley 600 compression test on all cylinders around 120 I have true duals and the pop comes from drivers side at idle consistent pop pop pop and that side of the exhaust is warmer than the pass side the pop is loud enough to drown the hooked aero chambers I'm lost adjusted carb timing all rockers seem to work also I changed to height distributor