Magnetic?
Mine looked exactly the same and rust was the first thought, but the metal was really corrosion free, untouched, just a little stained.
The 1/4 tank of 2+year old gasohol had left a really nasty smelly smegma everywhere inside. The fuel line & injectors were OK, so I think it was the...
I'd be concerned with the type cylinder in it, - pressed in steel, cast iron or plating - chrome, nikoseal(sp?), many others, and its fins.
A lot of Porsche aftermarket stuff is more advertising then engineering..
