Just bought an 05 GTO. I am the 3rd owner, but I guess the 1st owner welded in magnaflow mufflers and removed the mid-resonators (2nd owner had no idea until I told him after the sale).... I am looking to upgrade the entire exhaust system. I was going to go with a cat back magnaflow system or borla, but am I going to really see a difference in sound or performance?? - Or should I just throw in headers and put the muffler money to something else??

 

Do headers...Magnaflow mufflers are straight through, no restrictions...but help deepen the tone..

 

You're not going to gain any performance going with a catback, maybe 1-3hp at the most. Sound will change depending on what mufflers you get with the catback but personally I don't think speding $700 for 3hp is worth it. Spend that $700 on some headers and you'll get 30hp instead.

 

I agree^ I rather spend the money on some good headers and benefit waaay more than a catback why not go true duals??

 

I put a clutch in a friends 05GTO and the stock exhaust looked like at least 2.25 with an X in the center. I'd say stuff some headers on and try it. Might be ok with a stock engine?

 

Leaning toward kooks headers or american racing and a pair of cut-outs leaving the magnaflow mufflers the way they are.

Mid resonators are replaced with two separate pipes. Don't I already have true duals then??

 

you already have true duals on the 05. I would make sure you have some sort of crossover. add an X-pipe where that mid resonator was. The Stainless work's headers are really nice. I had a set on my 06 and they fit great. Borla sounds badass but if you've already got mufflers on it, I would save the money and put it elsewhere.