Low top end

Some reason as of last weekend I cannot get above 165mph. Doesn't matter what gear I am in the bike just won't go. Will redline in 1-4 but 5-6 are both stopping early. When I roll on the throttle smoothly it "feels" as though it is getting a bit higher but I didn't gps that run so can't really say for sure, but when throttle is thrown open it stops pulling and levels off WAY too early. Right now I am thinking TPS or fuel but keep thinking that I am forgetting something here. Yes I am shifting through to 6th.