Hey guys a new guy here and i do not drive a civic always wanted one but thats not what i ended up with. But anyways i have a friend who owns the Si he has the stock engine with V2 and is getting the GReddy Evo II catback. WOuld it be better to get 4-1 or 4-2-1. I do not know much of anything about the civic engines so help would be apreciated.

 

what does he use it for? for just around town use, the 4-2-1 header will give a bit more power in the mid-range than the 4-1. the 4-1 will give a little more peak power, which is better for quarter mile.