Even if it is it would be so little it would have no effect.I had edelbrock heads,stock heads and now trickflows all with dougs headers and have not seen any substantial difference between them (the stock heads and trickflows same headers same car).You have to understand the tech doesnt have a blueprint in front of him and there are production tolerances as well.If the engine is right,the mounts are right and the overall fitment is right it is the headers.
