I feel that you are grasping at straws here, but I'll try to grab a few with you. First, are the cam, intake and exhaust all set for that high of RPM?
Second, what happens when it gets to 7k? Does it break up and pop, does it suddenly fall on its face, or does it just run out of go like a black dog on a sunny day? If it is the last, I would be checking the ignition. Either timing or if it is running out of spark power. If the power loss is sudden or rough, then I'd check the valve train adjustment and valve float.