CM870 Aggressive driver

[bighank]

A customer of mine is complaining that his driver is driving the piss out of his truck, has a factor 565 ISX CM870 in it that has not be modified.
Owner wants to lower to horsepower rating to slow the driver down but I feel like this will just make the driver beat on it more.
Are there any other ways to compensate for an aggressive driver and prolong the engine life other than firing the obvious issue. I'm thinking something like tuning it to cut out fuel in higher RPMS or torque limiting or some other computer wizardry?