In Maryland they perform the OBD-II test. I know that it will fail with a primary cat delete. Testing is done every two years. It's just a pain to go to the muffler shop and pay a hundred bucks to put the stock pipes back on for a five minute test. I'd rather just get rid of the secondaries and be done with it. I just need to know if there is an advantage to Challenge or Fabspeed - vs just gutting or deleting the secondary cats on the stock mid pipe.
E90 M3 Jerez Black/Bamboo Beige 6MT - BMW CCA
Dinan Rear Exhaust, Secondary Cat Delete, Dinan High Flow Carbon Fiber Intake, IND Painted Reflectors, BMW Edition Grills