Been having the same issue with my 2007 zx6r over about 5 months basically bogs down after 8000rpm and won't build any further also very harsh on and off the throttle in the low revs (like a switch), when I bought the bike she'd been sitting for about 4 years and had rust in the tank. I ran it like this and realised it wasn't building above 10k rpm so I pulled the tank and sat vinegar in there for a few days witch removed most of the rust. I put a fresh fuel pump and filter in and it ran well for a few months however after siting for 2 weeks it began to develop the same issue bogging down at about 12k and progressivly getting worse until it wouldn't build past 6k. I then put a sealant kit in the tank and had a new pump, new plugs put in, I also had the fuel rail and injectors cleaned and tested. Bike ran good for two weeks before having the same issues won't build past 6k now. Not to sure what's going on, any ideas would be appreciated cheers.