f7 is a good pipe. ran mine for about 10-15 hours. sounds awesome and has lotsa peak hp, but it is a little weak in the mid and bottom end. not the best pipe for trail riding, but pretty good if you ride a lot of straightaways.
i'm running the shearer pipe now and it's got a lot more bottom and mid range power. i mean a LOT more!
sounds better than my old f7 too.