will using a catalytic converter decrease my hp w headers?
 

i was actually thinking of running an aftermarket cat converter to decrease some of the annoying loudness from my exhaust.i plan on running a header,cat converter & 2.5 round magnaflow muffler for my 75 repu,which actually has no need for a cat because its smog exempt.i just want to see if its worth the install to save me the hassle from cops and what not....btw it will also be running a 48 ida weber!:)

I don't know if it will hurt your repu very much since its N/A but I have a cat on my single turbo FD(396hp @14psi). it is one of the smaller metallic types but it didn't help with noise much on my car but I will be using another one on my next car since it does help keep my car cleaner since my car is silver its noticeable

if it's noise you want to combat, then why wouldn't you just run a presilencer of some sort?

that is also another option i was looking at,either some type of str8 thru resonator or just simply adding one or two extra mufflers...