I have a 1994 integra Si-VTEC, i'm still running the stock cast iron 4-2-1 header, the 2-1 section has 45mm piping and a 2.5" collector and is mild steel i think. I've just bought a DC JDM 4-1 header and getting it fitted on monday, will i notice much difference considering i already had the 2.5" collector with 45mm secondaries, i'm guessing i'll feel a lag in lower end and possibly not much difference in top end, any one done a similar swap before????

 

some one answer this is a good post but i have naever heard of a integra si vtec

 

its the jdm gsr motor
sir-g i believe

 

w/ any header, the freer flowing, the more you will lose in bottom and more in top you will gain, generally. the top end gains are not really noticable but they are there. the bottom end loss will be a little more noticable. w/ hondas, the bottom end will never be there but since theyre so rev happy, top end power is what you want