vectra X25XE engine

Can any let me know what the round metal cylinder like thing with the
electrical connection it is held on by 3 bolts it has 3 other thinner
bolts to make it flexible i think it also has another round metal part
inside with a spring i think its some sort of switch not sure though.
It is located on the top rear of the engine beside the black plastic
box with 2 black tubes going into it.

 

Don't know which way the engine is in the Vectra, I have an Omega, but
it's either the EGR valve (exhaust gas recirculation) or the ISC valve
(idle speed control). The EGR valve connects one end to the exhaust
manifold and the other to the plenum (big shiny thing on top of the
engine that distributes air to the inlet manifolds). The ISC valve has
a pipe form the air inlet rams going into it and then into the plenum.