Ok, just out of frustration I attempted to start the car again. After holding the gas pedal to the floor it started for about 5 seconds sputtered, backfired through the throttle body then cut off. I tried again and it’s acting like it wants to start but something isn’t there to give it that extra bang. I know 0 compression is most likely 80% of the problem. But why would it have started with gas pedal pressed all the way. Anything else I should replace besides head gasket and getting compression back in the engine?