For throwing flames, you need fuel. Either a very rich setting, or a injection nozzle which is installed after the catalytic converter.
The oxygen sensor of the catalytic converter will always get the fuel-air ratio around lambda 1, so you wouldn't have any surplus fuel left for burning.
Take an incection noozle of a K-jet Mercedes, put a fuel pump behind it and press gasoline through this device. Ad the spark plug and you can throw flames like crazy.
Need I have to tell you, that this won't make you any faster? Not in the Diesel, not in the 560 SEL?
For people who do stuff like this the website
The Jacky Touch...
might be of interest.
Look for the galleries and enjoy.
Kind regards
Eberhard