i needed the spacers for the high flow cat as well. when i first put the exhaust on (the 3") with the cat, i threw the light. found the fouler trick, the problem went away. i dont understand why it took a year without a light to show. now the thing wont turn off.

 

IF you have a 3" TBE swapping out the stock cat is not that easy (wont fit). You would have to replace the factor exhaust.

 

depends on the exhaust i suppose, but i have a 3in. works turboback and kept the stock cat cause next year is inspection time! do like evoboi said and remove the foulers, but i would also check the wiring. i nicked the rear o2 wires on my install, (the o2 sensor hit thedriveshaft tunnel), and i had to fix the wires. no light for me though. as i said, i have the stock cat in place of the test pipe for now.