I can understand that, no self-respecting car enthusiast would want anything but a manual with a car like a Mazda 3.
The
Racing Beat bolt-on exhaust is dyno tuned, adds modest gains (too small to feel but they show up on paper), only slightly louder than stock. Build quality is better than the OEM exhaust. It's the quietest aftermarket exhaust I've ever heard, no drone, silences high frequencies and sounds nice and bassy when you give it full beans. Think of it as an aftermarket exhaust for adults. They also make high quality springs with rates about +20% stiffer than stock.
PS: the stiffer rear swaybar reduces understeer and gives a more precise responsive feel to the steering. But it didn't mesh well with the soft stock suspension, causing some bump steer. Then I installed the stiffer springs and shocks, which matches perfectly and fixed that problem. It handles about as well as any FWD car can now, vastly improved from stock. But it's not track stiff, more like road/GT firm, perfectly fine on the street as a daily driver.