Can you log your Omex 200 ignition, what coil arrangement are running and at what dwell? At what rpm do you get the missfire, you need to make sure your coil setup is able to refresh fast enough? If the Omex 200 doesn't offer a scope feature and a logging function I'd be looking to scope the ignition under load on the rollers using a PicoScope, or even a good old Sun Tuner machine as this is the only definitive way to diagnose ignition based hesitation or misfires that do not appear at idle.

Under load, cylinder pressure increases, requiring higher voltage to jump the plug gap which exposes weaknesses in coils, HT leads, and plugs. Our old Champion plug tester had a coil, an airline fitting, and a pressure gauge for this reason. You'd plug it into the workshop compressor, slowly open the valve while watching the plug and pressure gauge, then record the pressure at which point the spark went out. Keep in mind peak cylinder pressure is where peak torque is arrives, peak torque and peak cylinder pressure under load are intrinsically linked.

If you've had the car on the dyno and you've recorded where peak torque arrives, you also know where your peak cylinder pressures occur. If the missfire appears at or arround the engine speed under full load where you found peak torque, it's a strong idication something on the ignition side is falling over.

However, you also need to elimiate a rich or lean missfire from your list of suspects, a lambda sensor is your best friend here. I'd also want to put a fuel pressure gauge in the car to prove/disprove your fuel pump is genuinely maintaining a solid supply to your carbs under full load, and at high rpm. Remember, the actual shape of the spark burn line on your scope reflects the chemical composition inside the combustion chamber.

A PicoScope, a lambda sensor and a fuel pressure gauge should be all you need to find your issue. As with all diagnostics, one piece of evidence is never sufficient, you need at least two, and prefferably three pieces of corroborating evidence that all point to the same suspect.

Good luck with it thumbs