I have an ek4 full fisrt stage!My car has a ramair carbon intake,a programmed ecu obd1.The exaust system includes a handmade 4-1 manifold,a catalytic tranducer 200psi and one medium as well final handmade muffler.Overall exhaust is oem diameter?I would achieve..bigger power and torque after vtec and better "turning" at high rpm!

What internal diameter of mufller and exhaust pipe do you reccomend to me?