To Start off, I have a 1999 Civic Si.

I bought the car with a Apexi N1 Dunk Megahorn/Megaphone Catback (Forgot which out, too hot to check under the exhaust). My Question is: IfI change the whole system to stock pipes but replace the resonator with a Magnaflow, replace the muffler with a Blitz, will I lose HP? I'm not planning on buying the Magnaflow and Blitz because I took them off from my other car. Also is it worth it buying a stock pipe or should I just chop off the system pipe? And would a 2000 Integra stock catback would fit?


Edit: Forgot to mentioned, I currently have AEM CAI and DC Sports Header.