Im currently in the works of my new setup d15b and JRSC ported by endyn running 10psi. I currently have a 2.5inch exhaust no cat, resonator and a magnaflow muffler very small 4 inch body with the 2.5inch inlet and outlet.Im wondering if the Chambered Apexi ws2 Muffler will flow enough or will cause to much back pressure. I guess what im looking for is the (perfect exhuast system) Flows well but isnt loud. I drive the car for HOURS to and from autoX events and it would be nice to have something when I get out of the car I can still hear. What options do I have or do I just live with it.?