what do you have to lose.
1997 and earlier does not have O2 sensors downstream of the cats. So when those cats are removed there is no downstream measurement to compensate for. 1998 and newer have downstream O2 sensors and will cause the check engine light to illuminate when the cats are gone or even bad!!!look, i didnt think a 98 neded the sims, but i have a 97 gts and no cats for over 2 years and no light ever! though the 97 and 98 was the same but maybe i am wrong. i can tell you that a 97 will not throw the light tho, this i do have experience with.
Yes you will need them. I threw a CEL a few time a week when I pulled the cats on my 98. There are conflicting reports but for $100 bucks what do you have to lose.
You can leave them in to seal the hole but it would be a cleaner job to just install a simple plug (local muffler shop) or some even use a cut off spark plug, it will keep your sensors good incase you want to reinstall later. But it is as easy as unplugging your 02 sensors and plugging in the sims, wire tie in place and you’re done.![]()