First of all, if your Corolla is still N/A a 3" exhaust is way too big and you will lose power and torque. 2nd, if you want real power it's time to turbocharge it. The turbo kit from turbokits.com is excellent. It's well made and very reliable. I've had mine installed for 2 1/2 years and it's been amazing. I just got back from a 3500 mile road trip and averaged 33-39 mpg each tank while having a blast in the mountains. Check it out.