147 TS clattering/pinging
Over the last few weeks, my 2004 147 2.0 TS has developed a strange symptom. The noise sounds exactly like the rattle you get out of a torque converter when it's on it's way out, a rattly,clattery type of sound. This happens whenever I change up a gear and let out the clutch, and also between 4000-5000rpm. All other times the engine runs smooth and sweet. There's been no change in performance.
It's a bit of a worry. I've taken the plugs out and cleaned them (replaced them only about 20k ago with NGK items) and the ends were a whitish colour, indicating that the engine is running a bit lean. I've since done the ECU/throttle reset and run a fuel system cleaner through it. The only mod is a K & N panel filter.
As a side note, I've always run this car on 96 or 98 petrol from BP or Z, so fuel quality shouldn't factor in to it. There's no check engine light, nor are there any fault codes from the ECU, before or after the reset.
Does anyone have any words of wisdom? Anything I can check?