I was 99% sure 2011 was only N55 and everything i am looking atbacks that up(ETK, Motortrend, Car and Driver, Edmunds). 2011 is when the LCI was introduced which also came the new engine. So i would have to say either you have a 2010, or a N55.
http://www.motortrend.com/roadtests/...e_first_drive/
http://www.caranddriver.com/reviews/...t-drive-review
http://www.edmunds.com/bmw/1-series/...est-specs.html (see here how in 2010 it says "twin-turbo" and not just "turbocharged" :
http://www.edmunds.com/bmw/1-series/...tyle=101200600 )