Rep Power: 0

I have a 1996 Civic Si I bought a few weeks back, which had the engine swapped with a JDM D15B Vtec. I've already racked up over 600km since and it drives and runs smooth. Problem is... it failed emissions today. I'm in Ontario, Canada for any Canadian's on the board.
So now I'm scratching my head on what to do, or what to check. My mechanic recently told me everything looked safe and sound. The kid I bought it from said he was running advanced timing with high-octane fuel. It has a custom exhaust header as you can see in the pic. So here are a few things I'm wondering, if any of you have ideas.

Kid I bought it off mentioned he hadn't done an oil change in a while, and he think's the spark plugs weren't good. I did an oil change last week, but spark plugs I haven't' checked... would it fail solely on this?
2nd, how could I tell if it was the catalytic converter causing me to fail?
And lastly, is there anything else I could check? It looks like it's running the stocks ECU for the 1.6L engine that was original with the car. Thanks in advance for any replies.

 
Rep Power: 518

Where's the report that tells you exactly why it failed?

 
Rep Power: 203

D15B is 1.5l pre 1996 and your running an ECU for a 1.6l? Did you read through the link I left you in your other thread?

 
Rep Power: 518

OMFG I just now noticed you used this LOL

I should add more to the line like "that sealer would be like firing a 90mm anti-tank gun at a squirrel......and still expecting to get a meal out of it"

 
Rep Power: 0

Yes I read the link, thanks for the reply. As far as I'm aware, 1997 and older cars still get the sniff test (in Ontario, Canada). Anything 98 and newer, they hook up to the ECU which I could understand would be a big fail for me since the ECU was for the 1.6 stock. See below for my results.

 
Rep Power: 518

Is the catalytic converter missing or hollowed out?

 
Rep Power: 0

It's there for sure, but hollowed out that I don't know. How could I check?

 
Rep Power: 518

I can tell if one is hollow or missing just by the smell of the exhaust, if running 87 octane gas. (high octane smells different to me)

I could also watch the rear sensor on a scanner and assess some relevant info....on a working, untampered setup.

Does it set P0420 cat code?

Is the rear O2 sensor on your car hacked with an adapter to space it away from the exhaust?

 
Rep Power: 0

I'll check that stuff out and get back, thanks.

 
Rep Power: 0

Checked under the car, couldn't really get a good look because it's near the front and in an awkward spot. I'll have to check tomorrow in daylight. But where the exhaust manifold is, there is a wire coming out of it. Could this also play into it? (btw, the drops on the exhaust manifold is just rain)

 
Rep Power: 518

That's the primary O2 sensor.......

Now find the other one.