Well, Stinky was definatly NOT a feral! He is a F5 Savannah that I was lucky enough to adopt. I know that they can make some very quirky noises so maybe the non-purring is another trait. He chirps too....most of his chirping is done in the middle of the night!
I'm going to keep my eyes on this guy, as it's always pleasant and reassuring to hear a cat purring away!