The Mileliminators are just to trick the PCM into "thinking" that the precatalytic converters are working properly. Hence, no P0420/P0430 codes. Other codes not related to precatalytic converters will still be recorded and the CEL will be turned on. If you have only the emissions PCM check, then with the mileliminators, you will pass the emissions PCM test, provided the inspector does not see the mileliminators.
As for the emissions tests with tailpipe sniffers, don't gut the precats or install headers if you have to deal with tailpipe sniffer tests. I know of two CEGers who had failed emissions tests due to gutted precats. They had only the main cat left.
In your previous thread, it was posted by a CEGer that some CEGers have passed emissions with only the main cat. Well, if you gut the precats or install headers and you don't pass the tailpipe sniffer, you will have to buy new precats, to the tune of $1,500 plus labor. Do note that you are taking the risk.
If all this sounds confusing, then don't gut or install headers until you are sure of what you are getting yourself into.
