Very helpful CC. Thks. Sort of learning my way forward, so this is helpful.

2014 MX-5 PRHT Mods: Goodwin Racing Roadster Sport Street Header with catalytic converter, GWR Helmholtz mid-pipe, GWR Super-Q muffler, Track Dog Cold-Air intake Versatune Basic tune Began getting P0421 Warm Up Catalyst Efficiency Below Threshold Check Engine Light about 2 months after a basic ECU F...