The only difference I know of between the 2011 and 2012 1 series was a 2012 LCI (facelift) update.
http://www.1addicts.com/forums/showthread.php?t=466003
BMW did change the engine to the N55 (from N54) and the transmission to the Dual Clutch Transmission (from Steptronic) in 2011 for the 135i. You could still get a 6-speed manual in any year.
Never heard of a special tune by the M division for the 2011 Model Year. If there was one I'd love to know about it since I own a 2011. lol
I read that the rear coil springs were changed from progressive to linear in 2011 for the 135i as well, as far as I know, that's it.