I've had my 05 FX35 since 09. My catalitic converter and "Y" pipe we replaced in 2013, before I knew performance exhaust could help my MPG. Now my rear flange rusted off. I'm investigating HKS Legamax mid pipe resonator/exhaust and Invidia catback. Will HKS give me any gains? I can have my stock pipe welded but my MPG is low.
