I also noticed that the 2011 StreetGlide seat is different than the 2010 also. Looks like they gave the passenger more padding and narrowed the nose for the rider. Also go rid of the textured look. I don't like it.
I don't know the part #, but I was also told it is different. If I remeber right there is a differnece in the grab strap and I don't know what else. I put a 2010 se flhx seat on my 2010 flhx and am very happy with it. FYI if for any reason you put the 2010 se seat on, youre original grab strap will fit if you want it to. The strap and buckles for the se seat are well over $100.