hey all!

Was wondering if anyone would have some insight into what might be causing my gpr to be slow.. i can only get 80km/h out of her at about 6300 rpm max, everywhere i look they seem to run around 100k's at around 7000 + rpm

- it has been recently rebuilt by previous owner... ( including the cylinders been sleeved )
- carbs where rebuilt and re-jetted by a reputable company to suit the engine been re sleeved.
- it was then given to another reputable company to do the fine tuning on the carbs which i think was done on a trailer backed into the water. ( apart from the lack of top speed it runs great nice and crisp throttle response ect..)
- I have also tested the powervalves by disconnecting the cables and opening them manually and achieving the same result.
- compression is good
- prop seems to be in pretty good condition and was told by previous owner it is a solas 13/19 (i dont enough to know)
- have installed a pump plug kit
- wave eaters on the powervalves
- also installed a works top loader grate
- + a ff exhaust in the rear which i heard you can lose 1 or 2 mph if you arnt running higher compression (that doesnt bother me cause it sounds mean)
- i am premixing my fuel with a fully synthetic oil at 40:1 ( tried unleaded and premium)

what else should i look at?????? this thing is driving me nuts and do not want to throw more money at it!