GM 8-pin hei weak spark

You for sure have a good heat sink and have not overheated the module? Monitor 12V while spinning a distributor to trigger it. They do not normally (at least GM) draw coil current unless triggered. Maybe the load is pulling down the voltage on the supply wire. "Usually" if something as these triggers at all, it's "good."

Did it ever work right? Maybe the coil is simply not compatible. Try a different coil. With a GM 4 pin and no ballast, even my old original Mopar coil gave a MUCH more impressive spark.