Thinking of going w/o cat. Does it affect the current tune? If so, how significantly affected?
You shouldn't be seeing MILs. Make sure it's snugged up all the way.I don't get CELs unless I let the car idle too long, (like 10 min.) and then even if it does come on, I simply remove the code and reset the ECU and it's fine again. This happens every few hundred miles on average (but only when it idles too long).
Right now, the car is running well. I've done at least 1500 miles with my Weapon-R header. Love it
You shouldn't be seeing MILs. Make sure it's snugged up all the way.