ive been getting CEL's with mine, not all the time mind you, if im pushing the car pretty hard and it backfires and pops thats when the CEL tends to come on.
This is on a 04 with a full turbo back and an up pipe also.

 

I have the turboxs stealthback w/ high flow cat, and it threw the cel after about 500 miles. I just did the mechanical fix, and problem solved. If you want to learn more about cel fixes, just do a search. You'll get a ton of hits.