Something I've noticed when turning the engine off on my SRi-T, theres like a whirring noise of something slowing down. Very similar to the noise the 2.2 makes when you switch that off.
I'm not really sure what to put it down to, I thought may be the turbo stopping after being on idle. But its quite a deep sound.
Er, tis a 02 model 2.0 Turbo 18k miles.