The number would be on the cat itself. Here is a picture of our GREEN cat.
Kooks,We are working on this. The strange thing is we have several cars Boss and GT's running our GREEN cats with no codes.
The advantage of the GREEN cats does go beyond the no CEL part. These cats come with a EPA number on them and are 49 state legal for emissions testing. The biggest reason to go with the GREEN cats would be the flow. Our new GREEN cats flow as well as no cat at all. We have done extensive testing and have seen this on the dyno. Brenspeed even runs our GREEN cats on their race cars because of these flow characteristics.