I know that, but Im talking dragsters since thats what everyone is bringing up. But even with that said, most race cars dont use just an open header, they have a pipe getting the exhaust to the side or rear of the car. Perfect scenario today. I took the car to the dyno and the guy said he wouldnt run it until the exhaust leaks were fixed because it would burn a valve. I thought he was retarded and I wanted it dynoed anyways, but i didnt tell him that. Its bad enough he has a monopoly on this area, only dyno within an hour and he charges $115 an hour!!