1999 Lumina - Random Cylinder Misfire only when hot

I have a 1999 Lumina with 35,000 km. Bought in 2005 with 13,000 km so the car was not driven much. 3.1 litre engine.

When the car is hot usually after 30 minutes of driving, it feels like it wants to stall when the accelerator is pressed. It backfires sometimes and juts feels like its not getting gas. When the accelerator is released it idles perfectly normal.

Changed the following : Plugs, wires Mass airflow sensor, ignition module, sent the computer out to get tested. The Catalytic converter melted as well, so that was removed and has stayed off for testing purposes. It is still doing the same thing now without the converter. I feel like I am just throwing away money. Any thoughts?