RUF is maybe the most famous "Tuner" (manufacturer, call it what you like) for Porsche, at least here in Italy.
Hamann is famous, rinspeed is well known...but when you think at "pimped" Porsches you mean RUF.

Maybe due to the number of Porsche "revisited", every videogame that doesn't have the rights for Porsche, asks to RUF (The latest: Gran Turismo 4, Enthusia...).

And i really do appreciate the job RUF does, the cars they "produce".
In my opinion it's the best way to speed-up a Porsche.

But still i'd prefer original Porsche presence because, as i said before, there's the importance of the brand, of the myth and legend of Porsche.
I don't care much to compare a RUF to a FERRARI, like i would have done with a Porsche.

And even if they build every new part they put on their cars, even if there's RUF logo, the car that is below is still a Porsche, and this thing will still make me say they're tuner, they're not car manufacturer.

As you can see, in every car you can put inside whatever you want, even the engine of another manufacturer, (just for example: Zonda has a Mercedes engine but it's still a Zonda, because they build the chassis, the project a brand new car, so they are car manufacturer) but if you build the chassis, if you project a brand new one, it's a new car. You build a brand new car, not a modified one.

Even at AMG...they're not car manufacturers, even if they re-project most of the parts and substitute them. They're still car tuners.
But in this case, official one.