I bought my 2005 mazda 3 and it has a mazda speed exhaust on it. What kind of horsepower does this add and whats the next performance upgrade i should add? I was thinking intake or a least a k & n air filter.

 

this has been asked many times, resulting in huge debates and really its not worth asking, so with that said it doesnt matter which bolt on you get next and you still have a 16sec car

 

I'll be a little more blunt; the Speed3 exhaust didn't enhance the performance at all, and adding a K&N won't add anything much either, errr, unless you're talking about the extra two or three horsepower you might squeeze out of your engine at red-line at wide open throttle (which will most likely come at the expense of mid-range torque).