I have a 2009 Cooper S (40k miles) with the tuning kit. Sense i Upgraded my intake to the DDW Ram air and Changed my oil and spark plugs . the cars is moving well but after the intake and plugs its been Misfiring on the top end when it goes into Overboost? Is it my Coil Packs or the Pesky High pressure Fuel pump? Its been running strong just starts to misfire in Sport and in the HIGH RPMS.

 

What CEL codes do you have ?

Thanks