I just bought a second 55. It is very loud inside the car. I am an old timer and I have never liked Headers. :tomato: I like loud, but out the back..My 1st car has a 327 ,Turbo 350, 273 rear and manifold and loud mufflers I love the sound. The new one has 350, turbo 400, 310 gear, shorty headers. I thought it had a 373 or 411 from the sound at 70. (No Tac) But I just checked and it is 310. Last night I took a ride in the back seat it is a littler better there. You can here the sound from the back. But in the front seat with the windows I do not like the sound. Super Turbo Mufflers. But the driver side muffler has a slight Crackel or rattle to it if I bump it. I do not see sign of a leak anywhere.Is it just the headers.