[backyard]

If you test light stays on constantly, without turning off at any point, while your pressing the gas, then it has to be something on the other side such as the coil, spark plug, plug wire, engine ground, or ignition module.

If you have 5.1 ohms primary resistance, that should be plenty. That sounds awful high just for a coil to me.
What kind of coil is it?
Does it say "External Resistor Required" or "No External Resistor Required" or something on it.

Unfortuneately it probably is the ignition module, like Lochlin says. He has fooled with enough of those to be an expert at those in my opinion.