can anyone tell me the difference in a 4-2-1 and a 4-4-1 header. i know that it means for a 4-2-1 that it goes from 4 to 2 to 1 pipe(s) but what are the performance differences? I am looking to put headers and a free-flowing exhaust on a '95 civic lx 1.5L 5sp. if anyone has any suggestions please post. thanks