 I bought 335XI with all the options, car has been a blast to drive, however in May 2008 my engine light came on took it to the dealership. Dealership had the car for 3 weeks after replacing both turbos and numerous other parts I got the car back but the mechanic did not know what caused the original failure. I started googling "335Xi twin turbo failures" there is a real problem with these cars overheating into limp mode especially cars that don't have oil coolers installed which mine did not I called BMW of North America 3 different times and got the same response, though I bought the 335XI with all options, since I had 17"  instead of 18" wheels I was not eligible for the oil cooler kit