Get a back issue of Sport Compact Car - December 1999 and read up on the SQUISH, BOOM, BANG article written by Mike Kojima as well as the section were they tested several headers on the SR20DE. All of your answers are there.FINSTER 187 said:I'm pretty much a newbie to performance modifications. Can anyone please tell me the difference between 4 into 1 Headers and Tri-Y Headers? I know Stillen's G20 headers (Part #508520) are 4 into 1, and HotShot's G20 headers (Part #NS3001), which is what I have, are Tri-Y. What is the difference in HP gain, if any?