Where is the diode placed as per my previous post?

If you are using a different circuit to that you published, how can you expect us to give guidance?

How do you dtermine that with the diode the spark is insufficient? How fast is the mcu pulsing the output? A 1N4005 is not a particularly fast diode so if you're trying to pulse at 1KHz then I can understand why the spark diminishes. Again, where have you placed the diode?

Also, understand how the ignition coil operates. You apply the power until the coil saturates - this normally takes a fixed time and is dependant of the volts applied and the inductance of the coil. When you remove the volts, you get the spark and the diode conducts forcing the energy out the secondary into the spark plug (as well as limiting the large voltage spike on the primary). Some systems measure the primary current and limit it others rely on knowing the characteristics of the coil and turn it on a time before releasing it for the spark. Leave the coil on for too long and it will burn out, don't leave it on enough and you'll lose spark energy. Which method are you using?

You really need an oscilloscope to see what's happening - otherwise you're in the dark. To design an ignition system that's reliable is not a trivial exercise. I suggest you use a known circuit or use a coil driver module. Also building this sort of thing on a breadboard it not advisable - high peak currents and high voltages will cause you problems.

What do you want the system for? What engine, what rpm?
What is the oem ignition module not doing for you?