1. Back in the middle 1960's I had an autocross car with a Ford V8-60 (135 cid flathead) midget racing motor in it (and Austin-Healy 3000 trans!), and I could get flames out of the sidepipes, even through glasspack mufflers, because the twin Stromberg carbs were set up a hair richer than they needed to be to work with the Isky full-race cam. I've also seen (at the same autocrosses) flames from the exhaust of aftermarket-exhaust-equipped early Porsche 911's, which also came from the factory set up very rich in their Webers (these same cars regularly burned holes in pistons from high-speed pre-ignition in the 1968 models, partly, I believe, because the new air quality regulations required them to be leaned out). I suspect that movie technicians make sure that their cars are set up way over rich if they want flames, but most race cars used to be set up very rich in the low speed circuits of the carbs in order to have the excess fuel cool the piston tops on overrun (braking for corners, etc.).

2. Nitrous Oxide serves only to provide more oxygen for the combustion process, so it is useless without some means of adding extra fuel, too. Early hot rod nitrous systems consisted of an extra FUEL injection nozzle, often fitted to an unused vacuum port on carburated American V8's, along with another nozzle to inject the nitrous, both controlled by some sort of electric on-off control from the dash, but I'm not really up-to-date on what they're doing on fuel injected cars of more recent vintage. I've been more interested in the propane injected VW diesel hot rods running on the Autobahns.