hey found a site that deals with propane injection for diesels, and methanol injection for petrol cars, both n/a and turbocharged, and seems a reasonably good idea for tuning.
take a look,
www.advancedfueltechnologies.co.uk - Home
the guy there is running one of his kits on a 156 at the moment, turbo applications could gain 25% with remap.
im not affiliated in any way, just thought there might be some interest.