Fusion Rough Idle

[Mattpegg]

I have a 2005 Ford Fusion 1.4 Duratec with 45000miles

since I had it it's had a rough idle and recently it's been occasionally stalling as you slow down at junctions. I have changed the plugs and leads and fitted a new coil pack, I have also changed the pre cat o2 sensor and cleaned out the throttle body none if this has had any improvement. I borrowed a diagnostic machine and run a live test on the 02 sensors the pre cat sensor fluctuates as I believe it should then the post cat sensor also fluctuates between 0v and 9v when I hold the revs at 2000rpm I am not sure if this is normal or not I thought maybe a problem with the cat as the previous owner only used to do short journeys. 

I just don't know what to look for next