Originally Posted by KIT

I think it is depends on what do you want. what do you drive most in your daily live? City or highway? Of course, change catback can increase a bit horsepower, but it would lose torque kg/m while in low rpm(e.g below 2500rpm), which means it is no good for driving in city. May be, most people don't really care about it. They will juz push a bit more gas and the sound from the new catback make them FEEL their car got more power..... in fact, it would be use a bit more gas and lose torque force while driving in city( many people feel their car got less power by the situation via stop-go in the city traffic light).....if your stang is Auto transmission, don't even think about changing large diameter pipe or a good catback. It will be worse than before.


Normally, the best way by increse the horsepower and also keep your car works good in low rpm is by changing the HEADER, the factory header is really rough inside. Which it is te 1st and most important part of the exhaust system. Normally people just waanna to make their car looks good by changing the mufflers or carback. In fact, the most efficiency is by changing HEADER. It is because it can good in both city driving and also in the highway. Most car engine got a better sound after changing the HEADER, too. It doesn't like the noisy mufflers' woo woo woo or annoying drone.

One thing we have to know is --> you don't change anything in your car is the best by using in city. BEST gas control & GOOD stop & go. This is the initial set up for most car factory. Sometime, especially in low rpm, exhaust system too smooth is not a good thing. There are value of the resistance in the system. ( I can explain if someone want me to)

SO, I said it is depends on how you use your car. If you use it mostly in the city, just change the filter (e.g K&N) is very enough. change the HEADER is the best way if you will use both city and highway. If mostly highway and high rpm, change the catback will let you see more result. OF COURSE, the BEST way is change both header and catback, but it cost a lot. If you do high rpm a lot, also can change short header and remove the muffler(should be very noisy).

The cheapest way to increase horsepower is by removing the factory catalytic converters. It cost the less but illegal(also should be very noisy) even though you really can see the result.