Problem with 98 GTX Carbed 951

[TLH101]

I need some help with this one. Today I took the '98 GTX, with a new top end and carb rebuilds, out for a little water time. Starts, runs, accelerated fine. Issue is, up to 43 - 4400 rpm, she cruises just great. If you try to go above 43-4400 rpm, it rockets right to 5900 rpm. There is no middle ground between 4400 and 5900. The speed goes up to ~45-50mph as well, so not prop slippage or cavitation. Max rpm is about 6880 at about 55+ mph. Altitude is 4400 ft. There are no other issues with the ski. I checked the rave caps and they are screwed all the way down, as designed. I pinched the vacuum line to the raves, with a hemostat, and there was no change. Everything is all good except not being able to drive at a normal "cruise" range.
Any ideas?

 

[IDoSeaDoo]

When's the last time you cleaned the Raves? Try to see what happens if you screw the rave set screws out and release some tension off those springs.

 

[TLH101]

Fresh top end, raves are super clean with new O-rings and gaskets. Tried in and out on the caps. No change.

 

[tobytd]

rave valves are moved by pressure not vacuum - test check valve?

 

[TLH101]

Have rave caps with viewing holes drilled in them to observe the valves. Working perfectly.