turbonick

I just bought an 07 Ultra 250X with 80 hours last week. Put it in the water for the 1st time over the weekend and it didn't run to the redline. It pulled hard and has very good acceleration but barely pulled away from an 8 year old Yamaha with 140HP. At top speed it was maybe 2 or 3 MPH faster. I was going around 54 MPH. At about 6750 RPMs the ski lurched and hiccupped. The boost seemed to stay right at 10 pounds. It was almost as if it had a rev limiter. It just floats around 6750 RPMs and flutters around there. How do I get the missing 1000 RPMs? The original owner says 7000 RPMs is the redline and that's how its supposed to be but I don't think so! I'll change the plugs and see what that does. Any help?