You should NOT need a new flywheel. Has to fire in the same place whether points or a module are doing the job. If you convert to a modern Stihl modulated coil then you MAY have to change the flywheel. Not with the NOVA II. You say you have spark, but do you have good spark? By this I mean will it jump an air gap of say 5mm and be a bright blue color and snap right across? If not the problem is most likely a weakened coil. One other thing make sure the ground from the module is being grounded out at the coil, not somewhere else on the motor.