i did a search and found that a 4-2-1 header would be best for a LS motor. would it be better if i went with the 4-1 instead if i have a built head?

 

a 4-2-1 is better since the b18b has a powerband in the lower rpms. you could use a hybrid or stepped design 4-2-1 header that will give you a greater powerband. you need to know what you want to give up when deciding on a header design(more top end or more low end or midrange). i might be of more help but i am tired and don't know exactly how your head was built.

i suggest going to team-integra.net and read ALL of the exhaust articles and if you still have questions then ask. you will learn a lot from these articles and hopefully they will answer your questions as to what is best for your setup.

remember it is better to know how things work and how they will affect your engine/car than to just put something on your car and don't know why or what it does. i hope that this helps