ALL headers aren't going to fit like you're dropping a rock into a big pond. Most always there has to be some type of modification because every car is not exactly the same. This requires a little work and head scratching but the benefits out weigh the stock exhaust manifolds. That's why they made headers to flow better. I get tired of people bad mouthing TTI saying "If they don't fall right in I'm not buying them."
I've heard the same thing for Hooker,Headmen, etc..
