I've had exactly the symptoms you are talking about with my Laguna 2.2dci - varying power, smoke, and a death rattle from underneath. ATS Euromaster diagnosed the cat (£400 to replace through them), as you could stop the rattling noise simply by holding it. I've had excessive smoke since i got the car, and tried having the injectors cleaned out, using stp, and the often recommended 'giving it a good flooring'. All this seems to do is bury the car behind in a cloud of smoke, before going back to the usual embarrassing smoking.
As the car has done 91k, and so is due for the 90k service, and needs the tyre sensors reprogramming and the back wiper replacing, is it time to just cut my losses? (and avoid a large bill)
Will replacing the cat have any effect on the smoke coming out the exhaust?
If there was a problem with the
, what else would i notice besides the occaisional power fluctuations?