Worry more about the number stamped on the side, not the year. The guy I bought mine from said it was an '03 also, but all I cared about was that it said X40F0X.
If it's stamped 35F01, then that will also work, too. But it means that it's from a GSXR600 or 750, and the guts of the muffler are made of steel, not titanium. Only a pound or so heavier. I happen to have one in my basement. Works great and I can't tell any difference in terms of performance or sound.