Recently, I put a DC 4-1 header into my JDM B18C in a 93 Si Hatch. Do you know what could be wrong because i was running 14.4 consistent before with just i/e and now that i put this header, it felt better but when i took it to the track, i couldn't get it down a 14.7-14.8 best time and thats that i put denso iridiums, magnecore wires, energy suspension bushing kit and camber kits aligned. A friend of mine told me not to change the header and leave the stock JDM one there because i would lose power. I didn't believe him when he told me but now i'm thinking its the header. Must be weird though. Can you all help or give any suggestions please????? I might even put the stock header manifold to see what happens.