Hi to all.

Bit of a newbie with diseasel problems so thought I'd farm the problem out.....
I have a Mondeo 2.0 TDCI 130 (2003 and on 122k miles) and last week while overtaking on the motorway the turbo let go big style, I took my foot off the accelerator to return to the middle lane and the car just carried on pulling up the hill (obviously running up on the oil.) Thinking that's never right, I knocked it into neutral and it revved straight round to, and beyond the redline and held there until it just cut out.
With the traffic being heavy I put it back in gear and just kept slipping the clutch to slow the damn thing down on the brakes until I eventually got passed several wagons and made it to the hard shoulder.
I swapped the turbo no problem, flushed the oil, cleaned the sump and the entire inlet track and it all fired up no problem.
The problems started the day after when I was driving to work - The car was down on power, maybe 15 to 20% and doing 44ish mpg at 70 mph where as before it would happily do 48-53 mpg on the motorway depending on how late I got up. The car also smokes heavily on start-up (blue) and also blows a load out if you coast along for a few seconds and then put your foot back down (also blue.) Just to add another complication, if you feather the throttle, the car hunts quite badly and jerks around until you either take your foot off altogether, or accelerate again.

My initial thought was I'd been stung on the turbo, but then got thinking about the time it spemt over-revving and wondering if this could've damaged the piston rings, or worse?

I know there are many things it could be, just after a few opinions.

Thanks