I buy some high performance filters from Fram for my XB12 at my local Farm and Fleet
the high performance filters have the same part number and just say "high performance" on the box. The Fram filters are the same size and work at least as well as the stock Harley ones. I've always run these because they are a wopping $3 for the normal ones and $6 for the higher performance
Here is their list for the entire line of filters they offer for Buell:
BUELL
500cc
Blast 2000-2008 . . . . . . . . . . . . . . . . . . PH4967
1000cc
Firebolt XB9R 2003-2007 . . . . . . . . . . . . PH4967
Lightning CityX XB9SX 2005-2008 . . . . . PH4967
Lightning XB9S 2003-2004 . . . . . . . . . . PH4967
RR1000 1987-1988 . . . . . . . . . . . . . . . . PH6022
1125cc
1125R 2008 . . . . . . . . . . . . . . . . . . . . . PH4967
1200cc
Cyclone M2 1997-2002 . . . . . . . . . . . . . PH6022
Firebolt XB12R 2004-2008 . . . . . . . . . . . PH4967
Lightning Long XB12Ss 2006-2008 . . . . . PH4967
Lightning S1 1996-1998 . . . . . . . . . . . . . PH6022
Lightning X1 1999-2002 . . . . . . . . . . . . . PH6022
Lightning XB12S 2004-2008 . . . . . . . . . . PH4967
Lightning XB12Scg 2005-2008 . . . . . . . . PH4967
Lightning XB12STT 2008 . . . . . . . . . . . . PH4967
RR1200, RS1200, RSS1200 1989-1993 . PH6022
Thunderbolt S2, S2T 1995-1996 . . . . . . . PH6022
Thunderbolt S3, S3T 1997-2001 . . . . . . . PH6022
Ulysses XB12X 2006-2008 . . . . . . . . . . PH4967
X1W White Lightning 2002 . . . . . . . . . . . . PH6022