The cat will lower the exhaust pollution numbers.

You can pass the actual emissions test w/o a cat if there's no visual. I was asking for the numbers on the actual results sheet. Those numbers tell you what you need to do to pass. My old protege would fail at stock timing, so I backed the advance down to 2* and passed. If you're that close, something little can mean the difference between pass or fail. With a programmable ecu, you CAN tune the car to pass as-is.

Maybe not. I've probably done fifty emissions tests and had a visual cat check once. They no longer look under the hood either. And there are emissions laws regarding engine swaps. Get the point? :ugh2: What really matters is what's coming out of the exhaust pipe IMO - that's what's polluting.

just buy a used cat...there is one on miata.net right now.

its how I got my FM cat...but then again I don't have to 'pass' visual inspection anymore, well...technically I do but you get the point

Yeah. Well, I'm just trading for the Jackson High Flow cause it's free, put it on there, fixing the tune to pass, and going back and passing.
Every place in my county does a visual check for the cat, even if they have to put a mirror under the car. Evidentally there was a huge bust on the local testing shops recently, that's what I was told anyway.

$50 "tip" and you can pass... you just have to find the right shop.

Yeah, I'd love to find the right shop! But I don't think that there are very many around here, and not any that are talking, that's for sure.

so what exactly didn't pass?

yea,show up with a $100,they woulnt even put it on the rollers.

Well, they did 2 tests, a 25/25 test (25 pounds of load at 25 MPH) and a 50/15 test (50 pounds of load at 15 MPH).
Here's the results:
HC-ppm - Pass (25/15) Fail (50/15)
CO% - Fail (25/15) Fail (50/15)
NOx ppm - Fail (25/15) Fail (50/15)
I can't remember the numbers exactly, but I do remember that everything was just above the allowed limit, except the one thing that did pass, and it was actually well under the limit.