rice slayer' said:
if you gut your cats will it throw you chk. eng. light on??. or would you better of just running new pipe with mil eliminators??
yes it will put the check engine light on. The sensors detect not whether or not the cats are ON, but whether or not they are working... gutted cats don't do there job (they dont "work" essentially) which is picked up by the rear 02 sensors.
You're BEST off (if that makes sense) by running gutted cats and MIL eliminators for normal street use (minus inspection of course, unless you're lucky and only have to pass visual, not the butt-sniffer test

)
Why? Because gutted cats will protect you from the all too common "cop on his knees with flashlight, checking for cats because he's pissed off your car is too loud", where as, striaght pipes ("race pipes") will just get you into trouble (most) of the time.
Regardless of what you choose, MILs will be required if you have, for any reason, non functioning, or non existent cats, or else you can stare at the check engine light (which isnt good, becuase if something really goes wrong, you wont know).