i'm planning on getting either an ep3 or dc5-s , but i want it to remain quite so i am planning on keep the stock exhaust, but if get headers without the rest of the exhaust will there still be any hp/tq gains, and will it still be pretty quiet?

 

bump

 

I can't speak for the DC5-crowd, but on the K20A3, shorty headers seem to provide a slight gain in the top end with maybe a slight loss of torque down low. Most people don't have any complaints once they get the i/h/e combo, though.

My guess is that you could probably upgrade the headers and midpiple (from cat-muffler), keep the stock muffler and still be quiet/smog-legal.