Oily cutoff valve

[Kneale Brownson]

I replaced my overrun cutoff valve (popularly known as the wastegate or
bypass valve) today because I've had the engine dying on deceleration
experience several times in the last week.  I'd replaced it in the spring
with a "good" used one I got in a purchase of a boxfull of parts because
the car was doing the same thing (dying at stoplights) occasionally during
the winter.  

Anyway, I noticed that the one I took off had oil on it just like the
inside of the Michelin Man hose gets.  Is that normal?  I didn't remember
the other one being oily last spring.

What fails on these things, anyway?