Thank you for your reply.
The mileage is currently just over 70,000 miles
Just a month ago it had a new dual mass flywheel fitted, The clutch plates and assembly were in excellent order so were not replaced.
The last recorded service was at 66,732 miles with an oil and filter change.
There is just the MIL light showing on the dash which comes on approx 5 mins after start up (assuming that something warming up) and stays on constant.
It does feel as if it is slightly down on power (143bhp) when asked to work hard and occasionally feels as if its misfiring or something on fuel line blocked. It does smoke occasionally (blueish/grey colour)
On tickover there does not feel as if much is blowing out the exhaust when you put your palm to pipe end and has a sound from the exhaust like a compressor chuff. I can hear the turbo whistle as you gently rev engine when stood still and feels like its working when driving with no black smoke. A few days ago i was driving steady away when all of a sudden a loud bank came from under the bonnet followed by blueish/grey smoke billowing from the back end followed by a loud knock, knock knock on tickover stood still.
I stopped the engine, let it settle a few mins, then tried re starting which it did no problem and ran as before after that. (fine but still with shudder and a quiet tick, tick, tick sound which goes when you accelerate harder and turns into the shudder.)
I have tried to give as much info as possible. Could this be something an injector out could cause or does this sound like a multitude of things happening all at once. I have had car looked at by 2 local garages (non mazda) one thought it be an injector at fault and the other could only find a fault code U3FF showing and thought a blocked dpf due to the lack of pressure blowing out the exhaust on tickover. I hope this helps as i fear taking car to a mazda dealer for diagnosis may lead to me being ripped off without half a clue before going in. Best regards, Mark. The car is a 2006 mazda 6 ts diesel estate 143bhp. Thank you