Welll if your region doesn't test for emissions or you know someone on the "inside", just get a mechanical fix to prevent yourself from getting any CELs. It take 2 - 18mm spark plug antifouler adaptors at your local autoparts store. Drill a 1/2" hole into one of them and then screw them into each other with the one with the drilled hole at the bottom. Then you take this and screw your O2 sensor into the bottom. Then take the whole thing and screw it back into the exhaust. This creates a spacer which fool the sensor into thinking there is a cat-coverter in place by reading less 02 at a cooler temp. I say if you gutted the 1st one, go for both and do the mech. fix.