Chevrolet: turbo 400, sized tires, drag truck

Question
I recently put a turbo 400 in my mud drag truck and cant figure it out. how come when the tranny is in park the engine seems to be under load?

Answer
Don;
did you raise the truck. yes , well it could be that the trucks  angle is way off and it could be throwing the computer and drive train  I'm not that up on the trucks drive train but  it could cause you all kinds of trouble if the frame and reared re not aliened. and over sized tires also.  ok