Hi just took my 2.2 direct to the steelers as its under full warranty, I have had a engine rattle for about the last week now, the car seamed under powered around the 1500 to 2000 rpm range and when under load.
When I put my foot down to accelerate in 2nd or upwards it rattled and seamed lumpy, the steelers found out that it was the auxillary belt tensioner that was failing to keep the belt tensioned at low rpm, they fitted a new one and the differance is a lot smother ride and acceleration and no more rattles.
Hope this helps someone