Exhaust

I have a 2007 Mustang Gt and I was wondering which is better between the factory exhaust or an aftermarket exhaust. I didnt know if an aftermarket would give me more HP and better sound

The Mustang has a sound that was engineered to exact specifications, or not, but they sound good as is. If you don’t plan to make lots of money from racing, the extra power or lack of it will make no difference. Those fancy air filters and intake pipes will make you feel a lot better than an exhaust that you will never see. K/N awaits your cash.

The stock exhaust on the S197 GT’s is not restrictive at all. It doesn’t become a liability until you up around 500 HP or so with forced induction. People swap out the mufflers to tailor the sound to their preference, but power gains are next to nothing in going to aftermarket mufflers in the 05-10 Mustang GTs. However there are gains to be had with a cold air intake AND a proper ECU tune to go with it. This is the reason you see alot of hand held tuners bundled with CAI’s for these cars. The ECU in the S197 GT is notoriously finicky when it comes to the fitment of aftermarket CAIs, and a proper ECU tune is a must. Also you can make adjustments to the Throttle-By-Wire with a tuner to make the throttle input more responsive. A CAI with a proper ECU tune can be good for around 15 crank HP with these cars.

Define better!

Modern cars have good clear exhaust and even the after market replacements are good.

You are more likely to notice a difference in the sound. There is it subjective. For me, I can tell you the less sound the better, but form many people it is the more sound the better, others like a specific sound.

Aftermarket stuff NEVER equals the fit or quality of the factory parts. Installing dubious aftermarket equipment WILL diminish your cars resale value…

In most cases yes, but not always. Some of the aftermarket stuff is miles ahead of OEM in terms of design and quality. Much of the time the bean counters get their way in OEM parts.