Slip-ons WILL give you a performance gain you can feel, will sound better than a full system imo because you get the stereo effect, plus they sound smoother than a full system, you will get a HUGE weight reduction that will make the bike feel a ton lighter sitting on the bike and in motion, will be a little cheaper than a full system and super easy to put on. Plus if you get titanuim slips you'll REALLY notice a weight diff ridng the bike. C'mon the 08 already has 170+ rear wheel horses.....unless your a dragracer you won't miss the few extra ponies a full system will give you. Unless you love tearing into your bike I'd just do the slips