| Putting LPG onto a modern EU4 emmisions certified car is going to be difficult to get running smoothly without the MIL lights coming on.
The mini has a turbo and direct injection too. You'd have to blow the fuel in pre compressor and run the full induction system fuel of fuel/air. This is a bit iffy as a backfire would take out the inlet manifold, intercooler, pipework and probably the turbo too (not to mention trashng the front of the car). The only way to get the fuel in would be to fit a much more complex and expensive port injection system. You'd have to build a new inlet manifold specifically for your car as you dont have any existing injectors.
The original GDI injectors are exposed to the combustion temperatures/pressures and without any fuel flowing through them they'll overheat and could be damaged so after a while I doubt the car would work on petrol at all and would cost a fortune to repair (GDI injectors are a different beast to std EFI ones)
Then you've got to think about how little fuel you'll actually be able to carry. The Mini boot is tiny, you'd have very little range at all.
Just buy a Dooper and get it chipped. I'm sure someone will get 150BHP out of the engine soon,  | 
