Donít know if this may help anyone, but you never no.
About 4 months ago my Engine light came on with no loss of power.
About a week later the TRC light started flashing and the engine started to misfire, I disconnected the battery after driving a few miles the lights came back on,
Went down the motorway one day and the car started to loose power, it got to a stage that I had to drive at the lowest revs possible because if I put my foot down it would slow down.
After advices I got a couple of used coil plug off ebay. I started the engine and unplugged the lead from the each coil plug and listened for any engine change when engine changed I plugged back on, when I got to the forth one it made no difference so I changed it for one of the used one brought from ebay and BINGO no misfire great. I disconnected the battery the reconnected it and restarted the engine, the lights had gone out.
I drove up the road but their was still a loss of power then the lights came back on.
The next day I called out a mobile tuner, he plugged in his computer and reset the engine fault, and found no fault.
So he took out one of the front oxygen censor that is screwed into the front Cat and told me to drive it. It was noisy but it made a big difference to the power, this meant it needed another piece or pieces of Exhaust.
I managed to get hold of a used Exhaust and started by changing the front Cat (to do this you must disconnect the steering and a few other bits and take it out the engine way) When done it made no difference to the power.
So I had to changed the Second Cat. This DID Fix the problem, The power was great and the lights were out. I drove for about 10 miles then the lights came back on, Fortunately I still have my front Cat so I changed it back all OK again. I have since drove about 90 miles and has been OK no lights. HOPE THIS HELPS
SO IT MAYBE AN IDEA TO GET THE EXHAUST CHECKED OUT IF ALL THE EASY BITS FAIL