Hi I have a 2003 Shogun Pinin which keeps producing the fault code P0421 - Warm-Up Catalyst Efficiency below threshold (Bank 1). Both O2 sensors have been replaced and the exhaust emissions are within the required legal limits. A Google search suggests this is a recurrent problem and a fix is available using spark-plug non-foulers (see
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. Unfortunatelythese devices seem to be unavailable in the UK. Can anyone help,either with the problem itself or with sourcing the non-foulers in theUK?