me and my buddies are thinking about building a custom exhaust for my car but using 2 1/5 inch piping with a high flow cat and muffler to create a little back pressure does any one think this is a bad or good idea

 

i've had a muffler shop do custom 2 1/4 exhausts on 2 of my cars only drawback is that its crush bent and not mandrel bent but it works and is very cost effective versus a $500+ system. you could get a universal muffler off of ebay for like 60 bucks and go to a muffler shop and have them repipe from the catback and install the muffler. it would cost 80 at a place i go to for that so thats a catback for $140