After info on fitting a msd crank trigger to a 360 magnum & working out t pulleys

check for slop in any of the areas it could occur, crank to cam probably not, specially under load, cam to distributor gear or shaft/gear wear yes. Module, yes...what about sticking weights? My guess is either distributor or electronics rather than gear related as any slop in gears/chain will go away when its all wrapped up with tension on everything, if it only did it on decel, I would look at chain or cam gear/oil pump drive.