N1 X Evolution 304 SS Resonated Mid-Pipe (144-KT01) by APEXi®. Material: 304 SS. The N1 Evolution Extreme is based on the proven performance basics of the N1 muffler. Optimum exhaust efficiency is achieved through the mid-pipes running parallel between the catalytic converter and rear muffler section. The H-style piping design was opted to equalize the pressure in both exhaust pipes. Apexi unique modular design allow the mid-pipes to be interchangeable with the factory OEM exhaust system components along with the rear section which is sold separately.