It also wierd how it only fades out when the hp an tq cross. If you are using an Eddie break, water break, etc on your dyno than the weight of the car being incorrectly entered can cause off readings because the Eddie brake simulates the load of the road based off the weight of the car. Maybe the tires spun on the second one? Do you have traction control installed, and is it wired to the engine in anyway to control wheel spin?