Changed coils, plugs, wires, intake gasket, sensors, and computer.

. Replace the Ignition Control Module (ICM), which the coils plug into.

. Ensure spark plug gap is correct. I would only use the ACDelco plugs that came in the engine.

. Apply dielectric grease to wire connections, porcelein and electrode portion of plug.

. Check for an exhaust valve being burned, which can cause misfires, if the problem persists.

My bet is the ICM is failing under load, due to heat. The computer and ICM control when the plugs fire.