In the old days that used to work but since NJ is now Emissions only for inspection I'm pretty sure they crack down on the emissions part of it because deleting the cat and not having a check engine light is not only step 1 of the job, if you can somehow space out the o2 sensors enough to not throw a check engine light you have to make sure your sensors have passed all readiness tests when the OBD sensor is hooked up.
This is for the guys that say "just reset codes then go through inspection since it takes 50 miles or so for the OBD to throw a check engine light", since although you might not have a check engine light after resetting the lights, you still won't pass readiness checks, which also takes about 3 hot-cold cycles of the key.
In theory, if NJ is truly Emissions only and does not do a visual inspection for the cat, you could pass the emissions test IN THEORY without any catalytic converter at all if you can find the "sweet spot" of o2 sensor spacing. From my VW days, if you only have one cat in place, you should be able to pass readiness tests and not throw a check engine light if you install one of these, and if they do not visually look for a cat
O2 Sensor Spacer
The spacer works so that the o2 sensor is taken out of the exhaust stream and since it "sniffs" less pollutants on the post cat section, the system is pleased and should pass readiness, without throwing a CEL.
EDIT: I do not condone tampering with Federal Emission equipment, however these are things I've learned in many years of trying to avoid check engine lights from glowing on my VW's. I always run high flow cats but essentially the spacer will work the same way as most high flow cats still will trip a P0420 code for catalyst efficiency since they flow much more than stock. You need to space out the rear o2 sensor a bit even with high flow cats in my experience to avoid CEL and still pass readiness.