My dad has a 97 cummins with about 160,000 miles on it and it is completely stock. He is wanting to put an exhaust brake on it because he tows a stock trailer around alot on steep grades. He thinks you have to change the exhaust valve springs when you do an exhaust brake. Is that true or can you just put on the exhaust brake and be fine. Also what exhaust brakes do you guys prefer. Thanks for any help. Sorry for the long thread.