You might get more replies if you posted in the General Discussion forum rather than here, but I'm sure most people will see it. The Saab takes to LPG very well and 260 hp on a 4 cylinder engine isn't a great ask as long as the components selected are sufficiently rated. Dual vaporiser installs are not uncommon or some have used something like the Bigas dual vaporiser which is basically two joined together. Never heard of LPG injectors made by Bosch though.
Obviously I know nothing about the regulations in Spain so don't know what they require and why they think it is too powerful. It may be that, as in Italy, most conversions are done on small engined cars that are already economical. They think that if you can afford to buy a powerful car you can afford the fuel to run it. In the UK it is different, most conversions are done on bigger engined cars to make running them viable. To buy a big, powerful car can cost no more than a small one, but it uses too much fuel for many people so they will convert to LPG to keep running costs down.
Thanks for your advice. I shall try to post it in General Discussion Forum