Hello Jetboy,
Ruf is "one of the most respected international sportscar manufacturers and suppliers of specialised components." As far as I am aware they are a manufacturer in their own right, just like Alpina.
Have a look at their company web site:
http://www.ruf-automobiles.com
Their 'base' is Porsche, but real Ruf aficionados do not call their cars 'Porsche' in the same way that Alpina owners do not call their cars BMWs.
I would very much like a Ruf (I could never afford one new, unless I win the lottery, but I always have my eyes open for a second hand one).
The Ruf CTR 'Yellow Bird' holds the fastest car lap time of the Nürburgring, well it did, I don't know if it has been beaten yet. See it at:
http://www.ruf-automobile.de/html/911_ctr_engl.html
Ruf also carry out retro upgrades of 'standard' Porsches... so you do need to know what you are looking at ie whether it is a Ruf from new or an after market modified one.
Which Ruf model are you looking at in Spain?
Regards & good luck,
Neil