Maybe I should have been clearer.
A car should not spit flames when being driven, as it does and will damage the engine. Bore wash, injector lacquering etc. As cool as it may look, there is a reason these cars have auto timing advance/retard, fuel mapping etc.
It will give a flame when revved to a high rev range then cut off as the exhaust port will stay open to scavenge the charge out of the cylinder as it thinks it's going to require a lot of cleaner air. On most videos you will notice it takes a while for the car to pop a flame (if it does at all) because (as has already been mentioned) it's pumping non required fuel into the cylinder and doesn't have enough time to do a complete burn.
Roughly translated - when being a tool.
