does any one have custom made headers on their civic. can any one tell me which style of header would be better a 4-2-1 or 4-1 because i am thinking of making them my self and can any one tell me a good diameter for the header pipes.

 

the main thing is that all the pipes should end up the same volume and allow for unrerstricted airflow at your disired power area,... you know what, read the article posted by sacs, "the myth about backpressure and why its wrong", itll get your brain moving in the right direction