550kW is more like 150mph, mate. Something is vastly wrong with the dyno figure or with your car once it gets to the track. Wheel spin plays three-fifths of bugger all difference in mph figures and can sometimes increase the final number so don't look to traction to find your missing horsepower.
If you're lighting up the tyres when you leave the line, lower the rpm's at which you drop the clutch. Play with tyre pressures a little (try dropping the backs to 15psi for the same burnout procedure) and check to make sure that it's not just the rears that are spinning. If it is and assuming you're back in 4WD mode, your transfer case may well be on the way out and not sending much/any of the torque through the front wheels.
Best of luck.