This is a known problem that occurs on a number of Plus 4SS cars

There is a solution, do not despair. You have a lovely car and this problem can be resolved. Where are you based?

Omex and Williams have developed new firmware and a new calibration for the ECU. The fix involves either taking the car or sending the ECU to Omex for updating plus the fitting of exhaust manifold wrap to make sure little heat is lost before the exhaust gas arrives at the catalytic converter.

PS, Welcome to Talk Morgan

Peter

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