He's correct, you will need cats if driven more than 5000 miles a year... Here's the kicker, how many miles was it driven in the past year since it was inspected? If over 5000 you won't be exempted from emissions this year, so be careful before you go ripping it apart just yet!!!! I went over 5000 miles this year so I'm no longer exempt, but mines almost stock, so I only have a visual inspection to pass since it's a pre '94. Just curious, why are you looking at putting the headers on? My '91 is a pretty strong runner and all I have is a 3" catback single exhaust setup. I'll probably only go the headers route if one of my exhaust manifold cracks, and even then I might just replace it. I have had bad luck with headers personally, and I'd be really cautious what you buy, all headers are not created equal. Some are just junk right out of the box...