Engine loads up at idle and dies erratically smokes heavy where i have to increase rpm to clear out in neutral. replaced plugs,plug wires,in-line gas filter,replaced water seperator filter,drain /replaced quiksilver oil in tank, I have always put seafoam in every tank fill last 20yrs. Runs great at full throttle, idles at 900 rpms. Leaning toward the coil pack test.trying to find out how to do that. any info I would appreciate it.