i have just a muffler installed....i would have gone for a catback if it wasn't so much money...and i was discouraged after looking at hp gains on turbo cars vs. NA cars....you can put any cheap catback or turbo-back exhaust system on a turbo car and gain double digit numbers, like 10 or 20 hp....if you have an NA car, you have to find the most finely crafted and tuned system for hundreds of dollars just to get a few hp, maybe close to 10 if you're lucky, but i think its like 5 to 8 on the protege....if theres a system out there that will give me 10 hp at the wheels, i might consider it for the 400 to 600 dollars....but in the meantime, while money is short, my replacement of one of the most constrictive parts in the exhaust system other than the catalytic converter, the muffler, for a hundred bucks is fine to me, gives me the sound that i like until i have an extra 500 bucks i won't be tempted to put into cams or pistons...not that i wouldn't love to have a cat-back to reach my cars full potential though