Now Puc you reminded me of something I hadn't thought of in years.
Back during the recession of the 80's the powers that be decided to try and save some money on gas by switching our fleet of cars at work over to propane. Well don't know who the 1st guy was to discover this but it wasn't very long before it spread like wild-fire. If you got the cars up to speed, say 55 mph, then bumped her up into neutral, shut the ignition off, let her coast, pumped the gas pedal like crazy and then reach down and turned the ignition back on to re-fire her.........BOOM! It would blow the bottom right out of the cadilitic converter. Well the fleet were new cars and of course they tried to get GM to fix them under warranty but GM blamed the company that did the conversions from gasoline to propane. The propane conversion company couldn't figure it out.......We went back to gasoline cars!