anything other than the stock engine will be very expensive to retrofit. forget the twin turbo N54.
even the engine out of a 330i will be difficult. you would need to find some way to reprogram the car to be able to control the new engine. it is not just a drop in replacement.
Past: 2001 330i ZSP/ZPP/Step
Past: 2004 S60R 6MT Sport
Past: 2007 335i 6MT ZSP/ZCW/322/655
Past: 2010 335xi ZMP/ZCW/ZPP/PPK/PE
Present: 2013 335i 6MT ZMM/ZDH/ZTP/3AG/494/508
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