DON'T waste your money on a new catalytic convertor. I just put a new one in my daughter's Toyota Tercel and it reduced the HC and CO to passing levels for California. BUT the NO was still sky high! Now that I've read the replies to your post, I'm suspicious of the injectors or a vacuum leak around them. The car has had a problem of burning up the spark plugs on the #1 & 2 cylinders. I had to install colder plugs on those to improve the life.

An IR thermometer gun can be used to most easily test your Cat...
there should be a substantial temperature rise across the cat.
Most smog shops will have one of these tools, and might help you out if they like you...

It was nice to meet you in person today.

A lean idle mixture can lead to high NOx. You may have to pay someone to set the idle mixture with the exhaust sniffer probe inserted before the catalytic convertor. Retarding the timing will often get the NOx to drop into an acceptable range.
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john

Following up on MittenHed's suggestion, here's how I look for vacuum leaks:

1) Take a propane torch and remove the nozzle/tip and replace it with a 2 foot length of flexible rubber or plastic hose.

2) Practice with the valve so you can get a modest flow of gas (not like you're raising a hot air balloon).

3) With the car warmed up and idling, turn the propane on and put the end of the hose wherever you suspect a possible vacuum leak (like close to each injector).

4) If the propane gets sucked in, the engine speed should increase noticeably as the propane adds to the fuel being burned.

It's best to do this out of the wind—and even eliminate the fan breeze by loosening the belt. But don't run it long with the water pump stopped.

First to your questions. The egr and the flame trap are not the same. The flame trap might be considered to be a pcv. The egr recirculates exhaust gasses to cut down on the oxygen available for combustion. You may have a bad cat, but first you should consider the thing that is the most basic cause of high NOx. This would be excess oxygen or a lean fuel condition. Look for vaccuum leaks. You can spend serious money on hardware when your whole problem is a broken rubber hose or a deteriorated o ring. Check the hoses and the injector seals. I burn lots of fossil fuel for a living, and in order to do so within a very restrictive air license, I have had to learn a lot about combustion. Some of the more coherently expressed ideas were posted in Opinions a month or so back.