the previous owner of the setup said that he hollowed out the cats and the check engine light May come on. After 4 days of driving, it happened. Anyone know if this is detrimental to the car or just the environment? Anyway to "defeat" this light?

thanks.

 

Some tuners offer an option to turn off the 2nd o2 sensor, which will eliminate the CEL due to having no cats. I'd call your tuner and see if they offer it.

 

Adam has a good point, I did