Hi, j got the following info from the french frend Jaques. according my knowledge the difference is only into the details specifications as it seems that Rune 2004 has the same.
ciao
Hannibal
91800-NRX1800-2005 91800-NRX1800-2004
Carburetion:
2005 PGM FI with six 32mm throttle bodies
2004 PGM FI with automatic choke
Front Brakes:
2005 Dual 330mm discs with LBS three-piston calipers
2004 Dual full-floating 330mm discs with three-piston calipers
ciao
Hannibal
91800-NRX1800-2005 91800-NRX1800-2004
Carburetion:
2005 PGM FI with six 32mm throttle bodies
2004 PGM FI with automatic choke
Front Brakes:
2005 Dual 330mm discs with LBS three-piston calipers
2004 Dual full-floating 330mm discs with three-piston calipers