Ernie,
I am not sure now what Thunder Hill would consider as to much power. Back when I had mine, the 530 horse was ok, but they inspected the suspension and everything closely to be sure it would stand that power. I know there have been some changes in the rules in the past few years but since I haven't been there for some time I don't know exactly what they may be now. I do know that mine would have been to loud now for me to run it there as they have set noise limits. I remember people racing there with open exhausts when I used to go. And I am sure that some of the other tracks may have rules that vary some depending on where they are and such.
Ron